ok since the computer has all the charts and everything for air fule ratio and all that. Dosent it get affected by parts that give you more HP? like a trany or head.

 

It wont change the presets with in the ECU if you add anything. There is a area that would be fine with a stock ROM chip but if/when you excede that you need a different ROM with different specs. Stock roms are good enough for basic bolt ons ex. header, intake, exhaust. If anything major you may want to change it out ex. Cams, p-p head, larger displacement, raising or lowering c/r, forced induction, NO2.