How will a header increase my HP? I read in teh SCC project SE-R that a header really won't deliver that much more HP in a SR20DE engine and it is not an essential item in HP gains. What kind of sound will an aftermarket header give me? I have a custom cat-back 2 1/4 " pipe with a Nakayama racing straight through muffler which delivers a nice deep low sound. How will a header affect that? also, same questions only with racing cams by either JUN or JWT? anyone with experience please give me your opinion?