3.7L vs 3.5L programming differences

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Originally Posted by Lex_Ordo

I know nothing of what is being discussed, and am always eager to learn more.
I've been asking questions about the GM Performance exhaust I had installed by the dealer, and read the posts regarding the PCM programming. I think, I will need to have the dealer service look into the PCM, and tune it to work better with this new exhaust.

I understand the EFI, requires the PCM to maintain motor function, and that the days of Carburetors, and pneumatic engine controls are gone, but how does one know the correct program for "re-tuning" the PCM to increase performance on any of these factory settings?

And more over, if the H3, for example can get better performance with a re-tune of the PCM, why doesn't the factory make it the best setting to start? Seems like it's counter-productive to build a car or truck, and set the PCM with programs that don't get the best performance out of the motor.

Anyone's thoughts?

Evidently you have not heard of CAFE or EPA. There is more to producing a calibration than making it fast(er) for someone. It is a find balancing act on these vehicels, with EPA being number ONE. The vehicle must pass all required emission (this includes the California air resource board- CARB requirements for CA and some other NE states). Second is the balancing act between fuel milage and performance. Yes, it is a Hummer, but GM wants to (needs to) get the best possible fuel mileage while keeping a decent power rating.