Hello all I put a test pipe in today. After about an hour or more removing the old cat. I put new gaskets in and sanded the flanges, but I still have a leak. Any ideas? It's like the gaskets just won't seal up. I also now have a check engine, but its just the o2 apm told me to bring it back to turn that off Any suggestions?

 

Are maybe one of the flanges where the dp bolts to the rest of the exhaust system (front or back of the dp) bent a little? Pics would help and where you may think the leak is coming from.

 

There is a smallmleak on the front and rear flange of the test pipe

 

Did you use that red gasket sealant stuff? I used a lot of if when I did mine and it's been fine.

 

Use muffler paste for the flanges. It hardens quickly.

Also, your Cel light, you will need to get a rear O2 spacer or anti fouled for that as ECU's determine if the cat is working or not.