Originally Posted by Togo

Stock Cats are NOT considered high flow. They are nearly the exact opposite. Anyone else's HFC (Stillen, Berk, FI, AAM, Zele, Amuse, etc.) will flow better.



From what has been said by Tony and others, this system doesn't seem real prone to rasp. With HFC and any resonator, 12" or 18", you shouldn't get rasp. It has even been said that the Straight X will not rasp either but we're yet to hear a sound clip.

If you are trying to "quiet the car down" because you are running HFC and a set of headers, yeah 18" might be better. It will just be a deeper sound.