I had to get a cat put on my car to pass emissions, but what I had the shop do was weld some flanges on the cat and y-pipe so I can just bolt it back on and off, and I also had them make up a pipe that I can just switch out with the cat. Now i'm getting an exaust leak between the flanges of the cat. and y-pipe. I took it back to them and they just wrapped some sort of exhaust pipe tape around it, and it seemed to as it got hot just melt it's self onto the pipe so it won't come off. It worked for about 15 minutes, then I can hear the leak again!! I think i'm just goona try and put two, maybe three gaskets in there instead of one, and hope that helps IF I can get that tape off of there. Any other ideas I can try???