do you have a resonator on the exhaust? how many? how big? if you dont have one, you can fit a 22'' resonator under there and it'll help with the sound.

is the type r header the usdm cast iron piece or the tubular jdm 4-1? big difference there.

hp for cheap isnt easy when you try to do it NA. every part has to compliment the next. you can do bigger cams, but then you'll need more compression. then you'll want a better header. then a tune. etc.

set a budget, set a power goal. then decide if you're willing to dig into the internals or if you'll be content with bolt on's.