Sorry for the late reply Mech, when I plug exhaust with my hand wearing gloves and using a rag, there is no change in sound at all and no build up in pressure. You would think if the leak was this large I could find it easily. The issue is the pipes have so much heat shielding on them. I need to remove the pipes and inspect. Just need to find the time to get it done, Hopefully this wknd I'll get them removed