I was attempting to remove the exhaust from the catalyc converter all the way to the tail pipe but i want to keep the catalyc converter on. Im using a 2001 chezy blazer 4 door and i just cant seem to find the right wrench to take the bolts off i tried a 15mm and it seemed too big and kept slipping. I went down to a 14mm and it was too small. Im pretty sure it has gridlock on it. Any suggestions on how to get this off without cutting or breaking the exhaust?

 

The nuts were 15mm on my 2002 Sonoma, but it's possible they're seized from time, rust, and heat. You might be better off just cutting off the bolts and replacing them when you add on the new exhaust, especially if the existing bolts are rounded now. For a few cents, cutting the bolts off and replacing them might save you a lot of headache vs trying to get the old ones off.

Another option would be to heat the bolt red hot with a torch, and then hit it with an impact wrench. There are lots of demonstrations on YouTube on the technique and timing for doing this.