GM-GMC: loss of power, spray patterns, gruman

Question
I have a 1994 gruman step van with a GM 5.7 liter throttle body V8 engine. It is hesitating and loosing power. Starts and idles perfect. Have replaced fuel pump and filter, new plugs wires and ignition system. Could be something with throttle body system? Please help

Answer
There are a few things you can try.  Use a flash light and look down the throttle body while it is running, you should see evenly shaped spray patterns from your injectors.  You can also try unbolting the exhaust.  A restricted exhaust can cause performance problems like the ones you described.  You can also check the timing. Base timing is adjustable in 94 and can also cause a lack of power.
Try a few of those things to narrow you search.
Hope this helps