Everyone that has anything other than stock components before the mid-pipe/y-pipe has the hiss. I think Motordyne found a way to mitigate it, but it is still there. I feel your pain though. I searched for exhaust leaks for weeks, lol.
Just for reference, I have the Greddy 20G TT kit. The downpipes (2.5" ish) connect straight to the F.I. TT-TDX (3"). My theory is that the difference in piping size contributes to the hiss as well as any places where the pipes split (in my case).
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 2007 350Z NISMO #0618: Zerolift | UPREV | F.I. | Greddy | Competition Clutch | Injector Dynamics | Aeromotive | Pioneer | JL
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