Originally Posted by AAM_COMP

The idea behind intake and exhaust mods are to move more volumes of air efficient in and out.
If intake and exhaust mods were done but OEM cats were left on, the OEM Cats would be acting like a kink in this system.
You will see definite improvement of whp gains after the HFCs.

Because of 370Zs dual intake system, compare to single on 350Zs, the intake kits are now about par with HFC, sometimes even cheaper.

It's your call, if you buy HFC, you'll eventually mod your intake system anyways.

Either way, gaining HP is better than not gaining any.
Catch 22, in a good way...