all i know is michael montgomery made 26whp with PRO1s, over his stock camshafts. He had a RSR HEader which might as well have been stock.

They DO MAKE A 2.5in DC header, its 4-2-1, and its a great deal for the price. If you can afford an SMSP or HYTECH BY ALL MEANS, but lets be realistic, most people arent spending $700-1000 on their H22 or B series header anymore.

PRO1s
DC 2.5in Header
Tune

Start there, im sure youll see gains with the Euro-R manifold and a bigger TB. But i prefer most people to start small an work their way up