I have had the AEM fail in the Supra before. It is not the EMS, it is the removeable eprom chip inside it. AEM will send you one for free. It takes 10 mins to change.

The AEM is a great EMS, made by GEM. I like haltech and Motec also, but if you already ahve the AEM, there is no reason to change. It is very easy to program, and has plenty of features.