Let's assume that you are in the U.S. Volvo changed the design of the exhaust manifold and catalytic converter for the 1994 model year, so 1993's design is unique to that model year only. I'm not sure what dealers will charge for a new catalytic converter, but I priced one at about $250 for a non-Volvo new replacement. I'm not sure what you mean by "a little loose", but if you have an exhaust leak at the junction between the exhaust manifold and the catalytic converter, good luck trying to fix it. I'm not sure how common this is on the 1991-1993 850's, but mine leaked, and after replacing the sealing ring and hardware, and trying high temp RTV, I finally just bought a used exhaust manifold and catalytic conveter from a 1994 model year, and replaced the entire system. Bolts right in, easy fix, no leaks now. All parts, including new gaskets and the heat shield were less than $300. A bit on the expensive side, but well worth it in the end in my opinion. The design of the 1994+ exhaust manifold with the flex joint and four bolt flange is far superior to the earlier design. Any year from 1994 on will work, but bear in mind that at some point Volvo added a second oxygen sensor after the cat, and an air pump inlet on the exhaust manifold. You can just get plugs for these if necessary.

Phantom