speedfreek

You will always have hiss with the VQ engines. Some say it is the design of the exhaust and flowing more air when you add HFC,TP, or LTH. The pressure is trying to be equalized at the X,Y,H pipe for whichever design you have. The Nismo exhaust I know seem to not have it as the other designs cuz it is an H pipe. The other is when you take off the stock cats and put on the HFC's the walls on them are thinner than stock allowing the sound to escape. Whichever theory you believe the sound is here to stay. I am guessing since ARK put out a HFC stating it eliminates hiss that they used thicker walls to lessen the volume of the hiss. I would hate to know they reduced the flow of air to reduce the sound of the hiss.

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