Solved! I posted this on another site also in the event that if someone has a similar issue they might do a search and find some information.
The exhaust brake now works perfectly! I sent the ECU (Electronic Control Unit) to Transmission Instruments in Flower Mound, Texas and they repaired the ECU WTEC II including the power supply. The cost was much lower that purchasing a new unit. $495 plus shipping instead of several thousand dollars. After chasing the many exhaust brake fixes for quite a while I became aware of the exhaust brake functioning ONLY when the trans was hooked up to an Allison diagnostic computer.
The problem has finally been fixed thanks to John and Judy Kopalek at Transmission Instruments. Transmission Instruments
