Last year, my exhaust was making quite a bit more noise than expected. The mufflers were old, so I decided to just buy the entire kit and replace it all at once. After I pulled the thing off (the easy part), it turned out that the leak was from a broken-off-in-the-front-bumper cat pipe. I half-assed the new exhaust onto the car with an exhaust adapter, grinder, and welder, and it's been that way ever since.

Lately, it's worsened. The cat, according to my mechanic, is non-functional. It still leaks a bit, and some new leaks have opened up in the header pipe. So for my next project, I think I might tackle the header pipe and catalytic converter. My question is on parts. On fcpgroton, I've found stainless steel cats. Worth it? (it's $20 more) I'm guessing yes, but it can't hurt to ask. Further, the header pipe has two variants. . .O2 sensor in the cat or O2 sensor in the pipe. The O2 in cat model is $80 less than the other. My current setup has it in the pipe. Will the current O2 sensor wire fit to the cat? Am I asking for trouble by either drilling and tapping a hole or drilling a hole and welding a nut?