I've got a 7.5 performance with PPF/GPF & have an exhaust (or manifold or something else) leak.
It's guaranteed to be there on cold start up to around 1800RPM (never over 1800) & dissapears when cold start idle revs drop to normal, it's occasionaly present on warm start, but never on hot. I've had a dealership & independant look at it & both said the exhaust look fine & has no leaks, although it just sounds like a regular "fut, fut" exhaust leak.
My 1st though was that that it might be EGR related as it's present generaly when an EGR valve would be active, but as far as I know EGR duties are carried out by B-Cycle & valve timing on this engine. I'm a bit concerned that the source may be more involved (expensive) than a simple exhaust leak & I'm starting to wonder about manifolds & what not.
Any ideas appreciated.