CK5 - The Full-Size GM Off Road Community

Ok so I replaced my head in my 1994 Chevy Beretta 2.2L about a week or two went by and the cat was clogged and would not alow me to go 15mph, so I had a whole new exhaust put on(it was about time anyways) well a few weeks go by again and she's clogged up again?? Im thinking something with my mixture or something. But anyone got any clues??? ANY HELP WOULD BE APPRECIATED...

Throttle Position sensor, O2 sensor outta wack? Sounds like your going rich, better hook up a OBD reader and see what the O2 sensor is reading.