What setups would yall recommend for a 07 g35x. I have a full catback, z1 y pipe and hks axel back and my car is still super quiet. i was looking into hfc but i just dont know if it would be worth it without looking to other axel backs first.

 

I'd look at test pipes if you're not worried about passing emissions. Just make sure they're resonated as to avoid drone. I've got the full FI exhaust including resonated HFC and my dB at WOT is about 6/10, so not very loud. There are some straight piped Gs out there that scream but they sound raspy and certainly drone beyond hell making the cockpit unliveable.
More importantly, to me at least, is that HFCs increase power and torque without requiring a tune.