ok so im working on a 19941/2ton 4x4 silverado 5.7 v8 tbi OBD1 truck
no one has obd 1 scanner so i havent figured this out.

ok anything above 1/4 throttle and it boggs down terribly n barely moves but wot it tries to go but still dont have enough power to get over 25mph. now when timing is adv to 25* then it gets to 1/2 throttle before bogging n has a bit more get up wot is actually somewhat driveable n can reach speed limits.

does not smell rich constantly.. only smells rich after it stops bogging down.

i replaced the ignition control module, cap, rotor, plugs, wires, throttle body, iac, tps, ign coil, map sensor, coolant temp sensor, o2 sensor no difference.

now if the iac is unplugged it dont stall at idle but when its plugged in i cant idle in gear or turn the wheel at idle or it stalls and has even less power.

also blocked egr incase i was bad with no change.

no service engine light either

it sat for a month or two then it ran like this.. ran 2 full tanks of fuel through it since then with drygas in first tank and seafoam in second

not sure whats left other than pickup coil fuel pump or electrical issue... n doubt its mechanical issue

 

I know this post is from 2012 but someone else might need an answer to this question. I replaced the Fuel pump and fuel filter in mine when it acted like this and it fixed it. Remove the bed to get at the pump very easy to do. Don't fight it with the bed on.