1991(90) Ford F-150 Stalling

Hey folks,
Need some help here if anyone can........
Bought this truck about 3 years ago for next to nothing. It has the 302 (5.0HO) and was in decent shape.
Over the last three years I have done the following repairs (in this order):
Replaced Water Pump Replaced Radiator Replaced Ignition Control Module Replaced Front engine seals Replaced Rear engine seals Replaced Transmission (rebuilt AOD by reputable co)
Lastly, about 4 weeks ago I replaced the valve cover gaskets (been leaking since the day I bought the truck, just finally got around to changing them) and while I was there, replace the upper intake manifold gasket and did plugs, wires, cap and rotor.
Since I did those things last month, this truck has run like NEVER before. The motor purrs, the idle speed is down to 'normal', plus I replaced a BUNCH of vacuum lines that were broken.
However, in the last week or so, I have had trouble keeping the truck running. It runs great when wide open, however at low speed (in-town driving) everytime you hit the brake - the motor stops. It doesn't knock and die slowly, it literally just stops running at around 1,500RPMS.
The check engine light never comes on, and there are no codes to read.
What is going on? The motor is full of oil. The radiator and water pump working perfectly. The ignition works fine.
Last might, I took off to run an errand, and ended up having the truck towed to a friends house. I went down a road and went to turn left, and it died, and it would not restart.
After it was towed, it would restart, and it just kinda runs like there might be a slight miss (but it is not real noticable.)
As soon as you take off, it dies.
I NEED HELP!!!
Anyone have any suggestions?
Thanks, BigBob
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Have you checked the idle air control valve, They carbon up and no air gets through

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Yes, I have. Clean as a whistle, works like a charm.
Any other suggestions?
Thanks in advance!
BigBob
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Hey, this may be a little obvious, but I would suspect an electrical problem like a bad ground somewhere.
Also, since in coincides with the brakes, a faulty brake booster could possibly be causing a vacuum problem.
Don’t know if you got it figured out already, or even if this would help, but here it is.
"Big Bob" wrote:

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