Sinister Performance, LLC.

Custom Chip / ECM / PCM Reprogramming & Tuning

For most GM Cars and Trucks (EFI only & for off-road-use only applications)


We are dedicated to tuning your vehicle's engine computer to attain maximum performance and the best drivability possible while keeping the powertrain reliable.  We don't only focus on Wide-Open-Throttle performance, we also focus on all aspects of vehicle operation aimed at making your total driving experience more rewarding.  After all, a properly tuned engine is a clean running engine!  While we specialize in vehicles that have engine swaps done to them, we also have a lot to offer those vehicles with bone stock engines or those with highly custom builds.  Mild to wild, practical to radical, we will do our best to get your vehicle running as it should.


Custom Programming Supported Car Platforms:


Custom Programming Supported Truck Platforms


Tuning Support for GM MEFI controllers (sold with popular RamJet crate motors and Marine engines)


Special Applications (GM modules only)



Basic (One-Time) Mail-order tuning service (click here for details)



ON-GOING Mail-order tuning service (click here for details)



Shipping Methods (please note we've recently switched to UPS as our exclusive shipping provider, and we no longer ship outside of the USA)


Other Prices


MEM-CAL ADAPTER NOTE: The mem-cal adapter is a device that plugs in between the computer and the factory mem-cal on most 1986-95 applications. The function of the adapter is to bypass the factory PROM chip on your mem-cal and force the ECM/PCM to instead read the custom programmed EPROM chip we will install onto the adapter board prior to shipping it to you.  It has recently come to our attention that some late 80's to mid 90's factory GM PROM chips installed on factory mem-cals are failing when we try to erase and reprogram them.  Therefore, we are now recommending ALL customers who are using GM OBD1 ECMs and PCMs that have removable mem-cals opt for the mem-cal adapter option instead of sending us their stock mem-cals to be reprogrammed.  If you wish to assume the risk, you can still choose to send in your stock mem-cal to have it reprogrammed but we will not be responsible if your reprogrammed mem-cal does not function properly in your ECM/PCM.  Anyone with a 94-95 3800 PCM (exc Regal) must use a mem-cal adapter, no exceptions.  Will not work with Cadillac 4.9 PCMs (ask for details).

For our ON-GOING custom tuning service customers: this mem-cal adapter accepts individual EPROM chips we can ship you which can be installed by you, the customer, without requiring you to ship us a mem-cal to be reprogrammed. Use of this device can save money and downtime when extensive tuning work is required. Additional blank EPROM chips cost $7.00 ea, but this fee can be refunded to you when you return undamaged, unused EPROM chips (if ordering more than one during the tuning process). Other restrictions may apply to your specific application, ask for details.

For our customers who have flash-programmable OBD1 ECMs/PCMs and OBD2 ECMs/PCMs - a PCM exchange program option might be available for you, email us for more info. (This exchange program is helpful if you can't afford any vehicle down-time. A core charge or other costs may apply. Limited availability.)

No refunds after 30 days.



OPEN FOR BUSINESS: Monday thru Friday, except for Holidays





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Prices/Policies Effective Jan 2021