I got an idle ECU returned as a core to upgrade and this core has a Zilla label on it. The case has also been opened and it looks like all the ICs have been replaced. I did not see any modifications to the circuit design.
It's funny that right after I bought my car, I did the same thing with my stock ECU thinking it may cure a high idle problem I had.
This is the first I've heard of Zilla doing this to the idle ECU so I guess not may were done.