Overkill Motorsports is proud to be the premier tuner for the GM 3900 V6. Improving performance and drivability, maintaining a healther transmission and improving fuel economy wherever possible are all high priority for Overkill 3900 tuning. It's with confidence that we know you'll enjoy Overkill tune above all others and your Overkill tune will help you enjoy your vehicle more than before. Whether you're an enthusiast car owner or consider yourself a normal car owner, these are differences you'll be able to feel and enjoy!

Features and Benefits:
  • Each Overkill 3900 tune is Made-To-Order based on your vehicle, with no extra charges for customization no matter what
  • Improved Performance on either 87 or 91/93 octane - Smoother quicker acceleration, sharp throttle response, reduced KR, typical gains of 10+ wheel horsepower on 91+ tune with normal bolt-on mods
  • Improved Transmission Performance and Life Expectancy - Includes fully recalibrated transmission shift pattern to improve upshifts/downshifts and reduce lockup bog, skip shift enabling, quicker shifting, lowers fluid temperatures
  • Removes P0420 code for high flow cat converter, loose gas cap codes, codes for EGR, EVAP and rear O2 sensor upon request
  • 2007-2008 equipped with AFM cylinder deactivation - 4th gear only tuning is standard, disable upon request to fix oil consumption issues
  • Many small features such as speed limiter removal, A/C compressor shut off under heavy throttle to regain horsepower, revised cooling fans with key off fan on enable, reduced traction control intervention and more

87 vs 91+ octane The non-AFM 3.9 V6 engine is less suceptible to engine knock/ping/preignition when compared to its peers. If you're purchasing a tune and looking for the most horsepower, we can do the most for you if you're willing to run 91+ octane, however if you're purchasing for a noticeable performance increase during daily driving, improved transmission life and behaviour, and fuel economy, the 87 octane tune will provide all the benefits you're looking for.
The 2007-2008 AFM 3.9 V6 is more suceptible to engine knock on 87 octane. If you're looking for daily driving improvements, you'll be happy with the 87 tune, and if you're looking to maximize your full throttle horsepower it's recommended you consider the 91 octane tune.






Overkill tuning is available for your 3.9 through our Autocal handheld. The Autocal handheld allows us to deliver your Overkill tune without you getting your hands dirty and with no relearns required; you to take the Autocal to the vehicle, read the factory file, email that file to Overkill, receive back and upload our Overkill tune. There are no physical installation and no relearns, you can switch between Overkill 87 octane and 91 octane tunes or return to factory tune at any time. Allows easy custom revisions as you add modifications, allows you to drive while scanning (datalog) and send us your scan files to further customize your tunes. You do need to install software on your windows computer to send tunes to the handheld, but no laptop is required.

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This flex fuel retrofit kit adds in the fuel content sensor from the most modern GM flex fuel vehicles into your 2007+ 3900 vehicle's fuel system. This sensor accurately measures the ethanol % in the E85 fuel in your gas tank, which can vary wildly from pump to pump, and allows the ECM to accurately fuel for that ethanol content. Kit includes a genuine GM fuel content sensor, black anodized aluminum AN fittings of the highest quality to ensure no fuel leaks, and a custom made wiring harness that requires no cutting or permanent alterations of any kind to your vehicle's wiring harness.

Pontiac G6 Owners - This kit, along with Overkill tuning or other custom tuning, will enable flex fuel on your vehicle. This means you can fuel up with E85 Ethanol and enjoy the increased performance it brings, and the lower fill up costs, while being able to switch back and forth between gasoline and ethanol whenever you desire. Anticipate upwards of 15-20 horsepower improvement with E85 ethanol versus gasoline

Chevrolet Impala/Monte Carlo - Your vehicles often come flex fuel from factory, as noted if you have a yellow gas cap. However, the old way of creating flex fuel enable vehicles was to set up a guesswork algorithm within the ECM; yes the ECM is just guessing your ethanol %. Adding in this retrofit kit will allow the ECM to see realtime accrate data on the ethanol % in your fuel. This will improve the performance and consistency of performance when running E85!

Note that this kit will not fit 05-06 3.5 G6s and will not fit the 2006 3.9 either due to ECM incompatibility.

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Highly recommended with an Overkill tune! The 3900 tends to run hot and you don't notice it on the gauge cluster. We've seen this lead to inconsistent peformance from vehicle to vehicle, and brings up concerns of oil life and engine life. When getting a tune from us, it's highly recommended that you choose to swap in this 180* thermostat! Typical operating temperatures will be reduced from 205-220*F to 180-195*F. It will allow you to get full performance benefit from your Overkill tune with no side effects for winter use, fuel mileage etc.

Tech Tip: This thermostat is borrowed from another application. It looks different than your OEM thermostat but is a direct fit replacement. Comes with a brand new Oring seal.





Available from Overkill Motorsport is the first and only larger throttle body for the 3900 V6 engines. This 76.5mm throttle body directly replaces the 71mm factory throttle body with the items included in this kit. The larger throttle body size improves airflow at higher rpm, and dramatically improves throttle response. Factory manifold inlet is already sized appropriately to take full advantage without the need for porting. All parts are brand new. Compared to $359 for our competition's factory sized throttle body, Overkill is a much better option!

Works with factory or Overkill tuning with no required changes. However, due to the vastly improved throttle response, if you want the best results, retuning the shift points is beneficial. If you have an Autocal we can provide a new TCM tune easily. If you have an Overkill module tune, we can send out a new Overkill TCM module tune for existing Overkill tune owners at no charge with a refundable deposit on the old TCM module.

Tech Tip: The clamping area of this throttle body is 3 3/8" versus 3" factory. On Impala and Monte Carlo, if you want to keep your existing air filter housing, use tubing part number 15824022 for a direct fit replacement to connect this throttle body to your MAF sensor and air filter box.

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For: Impala, Monte Carlo, Lucerne, Uplander or Montana

Once you upgrade to our 76mm throttle body, the small factory MAF sensor is a great item to upgrade with our upgraded options. We offer this kit to do both together and save you some cash! The larger throttle body and MAF work hand in hand to flow more air under hard acceleration and make more power. Larger 3.5" tubing and a large cone air filter make this a complete intake replacement. Great bang for your buck!!

For 2006-2009 Impala, Monte Carlo, Lucerne, Uplander and Montana, we sent a complete MAF replacement. It's a larger version of the factory MAF with a 4" inlet and 3.5" outlet. For 2010-11 Impala and Lucerne, we include a larger 3.5" MAF housing made of billet aluminum; your factory insert sensor you'll remove from the small factory housing and insert into the larger housing.

Kit will include:
  • 76mm Throttle Body Kit (same kit we sell separately, see for more information above)
  • Larger MAF sensor for 06-09 or 10-11, as specified above
  • 3.5" Silicone intake elbow including breather tube for PCV
  • Cone Air Filter
Tech Tip: Tuning is required for this kit for the larger MAF sensor. Overkill tune users with an Autocal will get an easy tune revision through email. Overkill module tune users can get a retune update, email for details.

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These are Brisk LGS spark plugs, a patented take on surface fire plugs developed by Brisk in partnership with Lamborghini.

A couple advantages:
  • The centre electrode is unobstructed by the ground electrodes
  • The spark event happens deeper in the combustion chamber compared to standard plugs
  • These plugs are made of premium materials, silver core and tipped which conduct electricity better than copper/steel/platinum/iridium used in other plugs
While these may look like another gimmick plug, they provide a noticeable improvement in throttle response and overall engine smoothness and can even provide some increased fuel economy under cruise situations. You'll find these plugs have been dyno proven to add 3-4 wheel horsepower over newer iridium plugs by multiple aftermarket Ford publications. I have personally put over 60k miles on a set of these plugs and unlike platinum/iridium plugs which show wear on the ground electrode leading to a large plug gap and reduced performance, these plugs looked like brand new and held their performance. If you need a tune up, I highly recommend you give these a try, you'll like them!

Price is $7.50 per plug and no shipping charge when purchased separately!