my exhaust is cracking right behind the cat. some material has rusted away so its not just a crack any longer. is it possible to weld a "patch" over the gap? i am in no position to get a whole exhaust steup. thanks in advance.

 

If it isn't on a stress point, you can try some muffler patch from an auto store. I can't remember the exact name, but it looks like a bandage made of fiberglass cloth. You wrap the pipe, then run the car which heats up the resin in the cloth, then it hardens. It worked a charm on my old beetle until I can get a better system.