I have an 88 5.0 tbi that starts right up but runs for just a second or two. Once it starts I can keep pumping the gas pedal constantly and it will stay running but kind of rough. After running it about five minutes by pumping the pedal I noticed a smell like medal getting very hot. I shut it off and look under the car and noticed the converter and exhaust pipes seemed very very hot. Could my problem be a clogged converter? I did change the fuel filter and it seemed to have pressure. The car has 55,000 miles on it.

 

If you can disconnect the exhaust in front of the converter, try that. If not you can take the O2 sensor out and see how much pressure is coming out of it.
Or if you feel like it cut the exhaust in front of the cat, and see how it runs.
Sounds like that could very well be your problem though.