Chevrolet Repair: Idle & Exccelaration, throttle position sensor, vacuum hoses

Question
My 92' 350 suberban has been having problems with excelaration, as in it feels like it is running on 6 cylanders rather than 8 and I have replaced one of the plactic injector caps and it is doing better but it feels it wont have all the power it used to and it seems to shift hard and sometimes a delaid shift and it tends to stall when i come to a stop or slowly excelarate.  Thanks for you help.
 Carl

Answer
Hi Carl,
If you haven't changed the fuel filter yet, it is a good time to do so. While there, catch about a pint of gas in a clean mason jar. Let it sit for a little while, and see if a little slug of water appears on the bottom, under the gas.
Make sure all the regular tune up items are in good shape...plugs, wires, vacuum hoses.If you have a vacuum gauge, connect it. You could find that the vacuum is low, which could be the egr valve pintle sitting on a piece of carbon.
The throttle position sensor is about next in line to check, but don't just run out and buy one. They can be tested.
Make sure the exhaust system isn't plugged. If it is, you should be able to hear it when under load.
Van