If you have an O2 sensor before and after the cat, not running a cat can play hell with the ecu, since the readings after the cat will be the same as before, the ecu will lean the engine to try and compensate for the readings.

Just buy a new cat from Autozone for about $55, or if you want to spend the money get a Magnaflow Hi-flow cat. There is some difference between the two, the Magnaflow is easier to see through. There is no benefit gained from running a 22r w/o a cat, you actually lose buy polluting your air more.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed