92 3.3L dies when hot

my 92 grand am with 3.3L runs for about a half hour then dies. I replaced the crank sensor and the ignition module. it'll turn on and run for a while then dies. it'll turn on but only idle, when i put it in gear it turns off ill try to give it gas but it'll start to back fire. i did notice that the spark plugs come out black and sooty. i was thinking maybe the converter could be plugged up but normally when a converter gets plugged up you hear forced air coming out of the exhaust.any one got ideas.

I would lean towards the Cat. When it does run, do you lack power at all?