Ive Done alot of research but cant find much for the exhaust system i have. So basically Im looking into getting some HFC. Want to get a good power gain and make my exhaust sound better but still stay legal. I Got a 2004 G35 coupe with HKS replica exhaust. Just trying to find out which HFC would have the best gains for this set up..

There is so many threads about exhaust systems it would take you a week to read thru them! Try it, SEARCH under subject HFCs you'll find the answer you're looking for. Search is your friend, any subject pertaining to our G35s. Once you've discovered what you want go to our MARKETPLACE under Vendor Exhaust for the best prices/delivery...
Gary

Most different brand HFCs are going to give you about the same gains (probably around 7-10hp). Test pipes might take on a couple more hp's, probably not noticeable, and good chance of flipping your CEL.

That being said, I have the Kinetix HFCs. They are definetly one of the more affordable HFCs. Great build quality, and never had a CEL. No complaints here.

Most likely it will be illegal to modify the emissions components in your state, but I believe all HFC's pass the sniffer test if thats required where your at. As already mentioned your not going to feel a difference between the different HFC's.

yea thats y i have to get HFC and not testpipes because i need to be able to pass that test. lol.
So basically try and find the cheapest HFC because they are all about the same?

Like Jhambor, I am running the Kinetix HFC. Once I installed this with my HKS HP, I noticed the car pull a little bit more since it opened the exhaust a little better. Kinetix HFC is not too bad in price. While I was in the market for HFC's, I also noticed that Berks was one of the favorites of most of the forum members. Nevertheless, I am happy with the results I got with Kinetix HFC, more happy than what I got out of my headers..LOL!!! Good luck...

Thanks, Ive heard that headers done even do much to our cars lol

^They don't, they do produce a nice exhaust note though.