GM-GMC: 1994 silverado running rough, throttle position sensor, brain box

Question
was driving down the road and suddenly loss power and sputtering. i have done plugs wires, rotor, cap, coil, egr, coolant temp sensor, air idle control valve, throttle position sensor, o2 sensor......  took it to shop and they unplugged the coolant temp sensor and runs slightly better. they suggested brain box so i replaced it as well.  it sputters and want to die at idle in gear.  on highway i can get up to speed and if i trounce on it it does accelerate.  also replaced coil and ignition module.....nothing has helped... slight backfire from time to time upon acceleration.......what else is there......i have had the fuel pressure tested and is ok......was one injector not spraying very well so replace that as well..does this sound like a vacuum lead.......this happened all of a sudden and i can't find any answeres. please help

Answer
There are a couple of things that can cause a loss of power like you are describing.  I would check your base timing first and foremost.  I have had trouble in the past with faulty distributors.  Other things that can cause power loss is a plugged or restricted exhaust or a plugged fuel filter.  Try a couple of those things and see if they help.