I've been posting about the mods that I have had done at MTI Racing.
So far those include:
Dynatech Supermaxx headers
Custom true dual cat-back exhaust (MTI Dual Shotgun Exhaust)
Rush air filter
Dyno tuning by MTI using EFILive
Here's the actual current dyno curve.
The increase in "peak" horsepower is "only" 20. But, if you count squares between the "before" and "after" curves in the 3600 to 5800 range (the range which both before and afer dyno runs covered), you will find that the AVERAGE increase in HP was 30 hp, and the AVERAGE increase in torque was 34 ft lb.
The 4.56 gearing I am running does not of course add any horsepower, but by compressing the gearing by 22% over stock, it GREATLY improves acceleration, especially in the 0 to 60 range.