By runs like crap, you mean no power?
Did you try to road test the vehicle with the exhaust disconnected, to eliminate a back flow problem?
If you did, and it runs like crap, then back to basics.....if driven with a misfire, that misfire could have taken out the cat.....
Check that f/p reg hose for fuel....try driving with the MAF disconnected......check fuel pressure, and spark on all cylinders with a spark tester......
Scanned for codes?