[Big Dave]

Your time and ingenuity would be better spent working on proven winners like fine-tuning your driving, improving aerodynamics, reducing weight and getting the gearing right. Maybe LRR tires.

The factory engine designers have resources you cannot begin to duplicate. I haven't seen anybody make any substantial (<5%) increases by diddy-wopping with the engine. Most of these engines (within the bounds of what the vehicle is) are pretty well sorted out. They have been at this a long time.