I got 1 cat off and I could see through it, no sign of being pluged. Is there any reason I can't use stainless steel nuts and bolts on cat? I don't know what grade SS bolts are. I worry that they might snap over time. Any idea if they will hold up? I was going to replace the front pipe to manifold gasket. I could only get one nut to loosen. The other one won't come off. I broke 2 extensions and gave up. I was going to use impact but didn't want to bust the stud. If you are going to remove cat bolts, have them torched off first. I spent several hours with air chisel getting only 5 of the 8 off. This job rates 7 out of 10 for a PITA.