need help fast...:(

okay guys...lol....was driving my 94 s-10 4x4 4.3 vortec to lunch today and noticed it was idling a little rough, it was cold out and i had just started it a few minutes ago, so i gave it a little more gas and it leveled out fine on me, no big whoop. alright, LATER, i was on my way across town when i noticed that it was idling rough again, this time it wouldn't level out, and at stop lights, gradually got worse. My engine light popped on and i pulled into a parking lot to check under the hood, everything seemed ok, but the motor was sputtering badly and the exhaust as well, i could tell by the fog/smoke from the exhaust and how it wasnt steady. So, braving it, i drove it home on the interstate, cruising to about 70, it ran smooth, but felt a little vibration from the rear that wasnt there before. light came on again.

heres what i've already changed that cant be the cause:
idle control valve
just recharged the k&n
brand new alternator

now, my dad who's been working on cars since i was born listened to it, and said that it could be the cat converter because of something he could smell, as well as the smoke not coming out evenly, like it was clogged. another thing he thought was it could be the mass air flow sensor, or fuel filter. I've got plenty of power up top, but at lower rpms it just idles like crap now. i know it needs a tune up but this just suddenly happened, i dont think its the fuel filter because i dont have any real hesitation when i floor the gas. i Am however getting crappy gas mileage, like south of 13 mpg. So, considering i still feel a light vibration from the rear, and my dad smells what he said was something like rotten eggs, i'm assuming its the cat, but would that throw up the light? or could it be that my mass air flow sensor just blew on me?

any help here would be GREATLY appreciated

pull the codes. a bad cat converter will smell like give off the egg smell. check the exhaust back pressure. if it was clogged i doubt you'd get up to 70. sounds like the egr is stuck take it off and clean clean it as well as the passages in the intake. there could be a lot of other possibilities for this one i'd also suggest checking the fuel pressure you might have a bad pressure regulator, this will saturate the cat convertor untill it stops working as well as kill your millage and make it idle like crap. check all the basic ignition(plugs,wires) stuff too.
almost every sensor can cause a rich condition so pull the codes. good luck

pulled the codes, came up with only one, 32, which in the gm book is the egr valve. at least i know what it is, but could that be ONE of the reasons for such crappy mileage? it was the only code it threw up. also, by looking at the location on the intake of the valve, it looks like besides the air cleaner i might actually have to remove the belt tensioner just to get a socket in, anyone ever had to do this on a 94 s-10 4.3 vortec? any advice on ways to do it without removing the tensioner would be a godsend...lol

you don't need to remove the tensioner. just a swivel and an extension. will have to pull it out though the top and it is a tight fit.

yeah egr valve take it off clean with carb cleaner or replace start vehicle with egr off rev up a few times this will blow out any carbon in passages stay back when doing as chunks of carbon will fly out