My exhaust system broke this week on my 1990 Bonne. One of the Rubber O ring hangars came loose, and the pipe broke right where it is welded to the front of the cat. Being the Cheap SOB that I am, I attempted to fix it with a new rubber hangar, some muffler repair paste, a sleeve made out of sheetmetal, and two hose clamps. IT worked perfectly for about 50 miles, but eventually I lost my seal. Basically the sleeve is still clamped in place and holding things together, but the muffler paste didn't prove very durable. Now it sounds like I've got a hole in my pipe, which is way better then it was when the pipe was completely disconnected. I may just let it go, and hope it gets no worse, as the car was cheap, and I've had it for a long time, and it seems like a lot of thigns are poised to break at once. But I'm leaning towards getting a professional to look at it, as at the very least I figure the cat needs re-welded to the pipe and I don't weld. Truthfully the car may have never had a new cat and might very well be worn out by now. How do the prices of a highflow cat compare with a OE type replacement? What about the rest of the system price wise? I'm kinda worried that the muffler shop guys will insist on putting new pipes on since I smeared that muffler sealant crap over a good bit of it.

If you passed emissions the cat is still good. If you want performance then buy an aftermarket High flow cat.
Otherwise a simple weld will do the trick possibly at a weld shop. A muffler shop is going to try and sell you a complete new system. Thats how they make their living.