94 Roadmaster 4L60E Transmission (200,000 miles)

Car runs and starts fine. When I come to a complete stop, acceleration or power is signifiicantly lower. Lasts until I shut it off.
If I turn it off wait 5-10 seconds and turn it back on, say at a red light, it runs beautifully. So I'm assuming an electrical problem.

Maintenance:
tune up
replaced raidiator and water pump (unrelated but whatever)
replaced throttle position switch
replaced ignition coil
replaced serpentine belt
replaced harmonic balancer
replaced fuel filter
replaced air filter
transmission repair (problem with that was skipping 2 and going directly to 3...the problem I have now seems like the car is having a hard time getting out of first, but don't read too much into this I'm a beginner)

Any help would be ****in gravy, this is way past my expertise.