93 S10 Blazer won't run, please help!

[khicks]

Vehicle description: v-6 with throttle body injection, 4x4, 196,000 miles
Problem: about a week ago it began having trouble; loss of power when trying to accellerate and rough idle. Now that I've been working on it, it's worse! I can start it up and let it idle, but after a few minutes it will get rough and die. It will be difficult to start for a while. If I try to rev the engine while it's idling, it will die.
Here's what I've done so far: 1) I checked the fuel pressure, and it's ok (12 psi) and replaced the fuel filter. The fuel pump was replaced last winter. 2) replaced distributor cap, rotor, and plugs. It was overdue for these anyway. 3) The only engine error code is 33, which refers to the MAP sensor, so I replaced it. No help.
What I haven't done: 1) replace the plug wires, these are about a year old. 2) check the fuel injectors. These were replaced about 3 years ago, at around 120,000 miles.
I considered that maybe the catalytic converter or something in the exhaust system may be clogged, but there seems to be a normal amount of exhaust coming out of the tail pipe.

Does anyone have any ideas where I should go from here? Should I go ahead and replace the plug wires and/or injectors? Thanks for your help.

[GMMerlin]

I would check the EGR valve for being stuck open.
Also check the pickup coil inside the distributor if it looks yellow and is coming apart or the magnet on your dist. shaft is cracked, this could cause your problem.
Low,weak coil output will cause this also.

The code 33 may be set because of the way the engine is running and not a faulty sensor.

[khicks]

Thanks for the suggestions. I'll check it out tonight.