So my boss has this 87 C1500 305 tbi auto pickup that he's been driving for a few years now. Northern farm truck so it has some rust issues starting, but it's only got like 87,000 miles on it. He had the distributor replaced, and shortly after it started really hesitating. (Stock replacement, no hop up go fast bits. "he likes to cruise") As in I've watched him trying to back out of a parking space and it seems like he's trying to idle out of it and he swears he's giving it gas. He's had the distributor taken out and replaced twice, timed by 3 different shops etc. He's getting single digit mpg out of it, and it has started doing it randomly while on the road as well. Always when at an idle or very slow speed. IE; sitting at a stoplight then thinking about shooting a gap in traffic to make a turn, parking lots.
I'm going to go out later and take a look under the hood for vaccum leaks. I'm honestly thinking EGR, Any other opinions?
My '96 behaved that exact same way. I removed, cleaned and re-installed the EGR and it solved it.
Dont forget to check for a faulty TPS.
Can you bypass the EGR by disconnecting it? I'm pretty sure if I remember correctly there is a 2 prong plug for the egr soleinoid.(sp?) I know that with prob cause a check engine code, but will it run that way? Been a LONG time since I've played with one of these.
Well atm we're gonna chalk this one up to over diagnosing. 
I took his truck on my lunch break to the store to see if it would repeat it for me. It wouldn't, so when I stopped I popped the hood to look around. There was smoke coming out of the trans DIPSTICK TUBE! pulled the stick, and it was pretty much dry... Non car sheeple. So I added a quart of ATF after driving it back to work, I checked it again, not even on the bottom of the stick. So I asked him when was the last time he checked his trans fluid, his answer was I don't know... "I assumed my boy was checking it when he was doing my oil." 
Good news is, it shifted fine, if a little higher in the RPM band than I would have liked, but it didn't feel like it was slipping when I got on it a little on the way back to work. Granted I didn't get on it and stay on it too long due to A. the speed limit is 45, B. big freakin truck that I'm not sure how the brakes are, and C. It's not mine!
Did realize I got way to spoiled driving tiny cars that turn on a dime when it came time to park it. HOLY CRAP that thing feels HUGE!
