Hello Guys,
Since i've installed my long tube headers (Texas Speed 1 7/8 with Offroad X-Pipe) i've notcied that (while having a tune with CFCO and DFCO enabled) while shifting or while on decel (as soon as the DFCO kicks in) i've got a sound that sounds exactly like an exhaust leak (an hissing noise).
If i flash a tune that has DFCO and CFCO disabled, that sound completely disappear, both on decel and shifting as well.
I've double searched for any leaks signs all over the exhaust line (they have been installed professionally and with factory new OEM gaskets) and could not find anything.
Also, i've noticed that when i have the NPP flaps closed that sound is really subtle, while if i have the NPP valves open, it's much more prominent like is actually coming from inside of the exhaust and not outside.
You can hear that sound on this video at 1:03 (not mine, but my same exhaust setup)
https://youtu.be/-a6PmsEUMOU
Any advice would be appreciated.
Alessio