I have to say after researching for weeks and reading these boards, I finally went with the hot shot header for my 04 spec v. I just had installed today and everthing turned out perfectly. No service light (relocated 2nd 02 sensor with included kit) and sounds great. Not too loud at cruise speeds. I have a magnaflow cat-back exhaust. I am however going to replace the resonator that came on the cat-back to the next largest (18") to tone it down a bit when on the gas.
To date my Spec houses the following:
Hot Shot Header
AEM cold air intake
Magnaflow cat-back exhaust
T-REX Billet front grill/bumper
Brembo brakes with Hawk HP pads (low dust)
Sony deck with 1000 watt Pyle amp
JL audio sub
pioneer 6.5 4 way for front and rear