92 350 EGR question

I am not sure if my EGR or the solenoid needs replacing or not. It runs fine when cold, sorta, but when it gets warmed up when driving about 25 miles an hour (automatic tranny) in second gear or third gear it really starts to chug. That is the only time it does that, I have also found that it does not accelerate as fast as it used to.
I have replaced:
cap, rotor, plugs, wires, pickup coil, fuel filter, timing checked.
getting a little frusterated at this point. :banghead:
any help would be greatly appreciated.

Engine off, using a vacuum pump, apply 18 Hg of vacuum. Start the engine, the vacuum should be zero and the EGR valve should have closed. Replace if it does not hold or drop to zero when engine is started? Also replace it is does not close when started.

TBI side of the solenoid should hold vacuum (engine off), replace if it does not.

Other things to check for poor performance when warm:

- clogged cat or exhaust
- fuel pump or relay (check fuel pressure)
- heat riser valve in air cleaner (should close when engine is hot so only cold air enters TBI)
- bad ignition coil
- timing chain

//2000CAYukon

I forgot to mention I did replace the ignition coil and the fuel pump. Also when it gets wormed up and I am either pulling a load or really getting on it the altertator light comes on and the needle drops and so the performance goes way down. However since I replaced the ignition coil and the pickup coil I have not experienced that problem.
Again, any insight will be greatly appreciated.

well it looks like the EGR solenoid was the problem. I replaced it and all the problems went away. runs great now.