TBI Surging Idle hesitation off idle

[pseudomike]

Any help appreciated....
'91 TBI 350, starts and runs fine when cold. Runs fine when warm but has a hesitation that will almost stall the truck just as you crack the throttle. Give it a little more pedal and it takes off like a bat outa hell. I can simulate the hesitation even when it is in park. It is almost like a dead spot. If you drive it mashing down on the gas it runs fine all the time....but once you let it find the hesitation the idle surges in park.

The motor only has about 15K miles on it. It has the Edelbrock performer TBI intake. I mated it with an oversized rebuilt TBI from RV morse machine and a chip from tbi chips. It ran graet for a while and now... I've sprayed and sprayed looking for vaccum leaks with no findings.

So far I've replaced

IAC
TPS
Injectors
Walbro Fuel Pump
Fuel Filter
Temp Sensors

I checked the timing and set it to Zero (yes I umplugged the wire). The cap, rotor, plugs, and wires are all relatively new and it doesn't have the classical ignition problem skip.

I'm pretty much at wits end with it. It drives fine 99.9% of the time until you find the dead spot. If it were more erratic I would suspect ignition or vaccum but it runs great except for just as you crack the throttle.

Any ideas?

 

[Thunder]

Bad idle and lean on acceleration could be a EGR valve stuck open or EGR solenoid bad. Might try pulling the EGR and cleaning .Make sure it is closed at idle.

 

[British Slave]

Not trying to hijack the thread, but what is the cleaner of choice for cleaning the EGR valve?

 

[pseudomike]

I'm thinking gumout or some other carb cleaner as it's just carbon.

As an update i replaced the EGR solenoid and the hesitation is gone. It runs and idles much smoother. The is still a little jitter in the idle 50-100rpms. It sounds like the alternator is really drawing on and off causing it to fluctuate. It does not do it in gear. I'm not sure if this is normal but it's running well enough to drive. I think I will get an aldl cable finally and try logging it.