GM-GMC: 1992 GMC 2WD 350TBI, mid range, parking lots

Question
Hello, I have a 1992 GMC with 187K miles on it. I have noticed some sort of miss or a stumble in the mid range rpms..the truck fumbles a bit at idle under a load(A/C, PS Pump) but I notice the miss mostly in parking lots when little to no throttle is being applied. I changed the cap, rotar, plugs and wires..and the problem still exists. A friend of mine was a tech for GM for 15 years and as soon as I explained the problem to him he said it was most likely the distributor assembly. Your thoughts?

Answer
The distributors have been known to get cracks in the pick-up.  You will need to remove the distributor in order to disassemble it and inspect it.  In my opinion if you are going to remove it, it is just as easy to stick a good used, or known good one back in, set the timing and see if it fixes your problem.
Hope this helps