How did you arrive at your "ultimate" parts list build up. How do you know the 2.5 exhaust will work better than a 2.25? What about the headwork? Is porting necessary? And finally, the cat, what about a test pipe?

 

Let's just say I've seen a few dyno graphs over the years.

The headwork's not necessary but in a built motor with high CR and cams and such it's good for about 10 hp. Why not, eh?

Stock ITR's gain power from running 2.5" exhaust, a built motor making more power should go with it too.

I like to keep cars street legal, hence the cat. If you don't care about emissions testing run a straight pipe, but a good hi-flow cat isn't much (if any) of a restriction.

 

I'm just trying to figure out the steps to building an engine, but I really should focus on my car. Aparently I've got to buy "aprons" for it that cost $300 each (2 sides)