Originally Posted by spiderman

exuse me for being retared semtex, as this is new to me. Can you please explain the difference between the Stillen exhaust and the need to put HFC's with it. I thought the Stillen is a full bolt on so there is no need for HFC's??? I'm looking to replace the stock exhaust when my Z comes in and thought putting the Stillen on (instead of the Nismo) would be all I needed to do. I'm just looking for some better sound, if bhp comes too, all the better. I'd appreciated some education here ... thanks!