I plan to eventually tt my 03 coupe and am looking to get it to the ~500hp range. I started with air intake, then got a header back exhaust with test pipes. With the test pipes on I lost a sizable amount of power due to lack of back pressure. With the stock cats back on the power is back. My question is what is a good order to follow so I don't run into the same issue?

I have upgraded cams and pelldulum spacer waiting to be installed.

 

if your going FI save your money the work from there...

 

You realize that the 500whp club is generally found around $20,000+ right? Could easily be more. And not likely, but possibly less if you find great deals and do a lot of your own work.