i posted this once before but still chasing this noise. It sounds like a exhaust leak at the head under a load at low rpms but I don’t see any burn marks around the header flange. No ticking at idle. Second gear low speed under a medium load and this terrable sound almost like one cylinder is leaking exhaust. Don’t see anything around the flange or collector. It did it with corsa cans and no cats and now I have stock NPP cans still no cats and it still makes that noise.

this sound only happens when you are on the gas at low rpms and you have the engine under a load. It’s most apparent in second gear. It’s loud and has a glass pack muffler sound but coming from the engine area. Thought it was because I was not running cats but I talked to others who don’t have them and they don’t have this sound.

I did the test with the vacuum blowing in the exhaust pipe and spraying soapy water on the leaking area. It was foaming bubbles everywhere. I read that the GM gasket was the best but when I removed the gasket it was the same GM ones I ordered. I didn’t see much burn marks around the head. Is there a better gasket.