I have a 94 blazer tahoo with the 4.3 vortec, it ran great till i went out 4x4ing one day, when i was taking it up a steep climb I bounced in and out of some nice sized ruts and it kiled the engine, got it to start again by pumping the peddle as i turned it over and got it home, I took off the EGR valve and it had a big peice of carbon stuck in it, so I cleared it and put it back on and it ran great again, but then it started acting up again, running really rough, so i cleaned the EGR vavle again and it ran great again, after doing this about ten times it didnt help it anymore, no carbon build up, just running ruough all the time, no power, slow to get going, terrible fuel millage, but it still drove and i couldnt afford thee new EGR valve so i ran it rough for a couple months, I just got the money to replace the EGR valve and it didnt fix it, helped a little but not really, its smoking worse now and is still running rough and is guttless.. Did i mess somthing else up by chance by running it like that?

 

One common problem to look for is a leaking fuel pressure regulator. You can visually inspect it by removing the "vortec" cover from the top of the plenum and removing the diffuser (I think thats what it's called) which is held in place by 2 screws. It's the round thing under the vortec plenum cover.

Once that is removed, you can look though the hole with a flashlight. What you should see is an evenly carbon coated intake. If it is nice and shiney on one side your regulator is leaking allowing excessive fuel into the intake causing flooding, poor fuel mileage, lack of power, etc.