just look thru the "Naturally Aspirated" thread... there are hundreds of post on BPU mods for the NA. Intake and Exhaust being the majority of these, there are also threads about turbo conversions... have a look down the list. i'm sure you'll find what you're looking for. if you have anything specific, just post. take care, good luck.
there was a post a couple months ago about "what can we beat" or something like that... a list of Road Kills by the all mighty NA. enjoy