Ill give you guys the short story

I own an MY98 wrx auto, i was driving along the freeway in peak hour traffic when i fealt a clunk and the transmission appeared to die. Transmission dude came to the conclusion it needed to be replaced, i replaced it with a 4 speed jatco auto transmission. Have now noticed an intermittent fault with the transmission. Sometimes when driving slow, like in peak hour traffic, the gear doesnt change up, so im left there revving 7k in first, not real good for my car, and making hardly enough power to do the speed limit.

The transmission dude has done all his testing and is yet to find anything wrong with the transmission, he says he thinks it might be an ECU problem, i never had an ecu problem ( other than it needed a tune) before the transmission went. His next test is to run the car without my ECU with his external computer to see if the fault re-occurs. This is an extremely time consuming process. Please comment and post your thoughts on this.

Thanks