I think the ZOOM is controled by the inductor valve between the two halves of the intake manifold. Sometimes it does its thing and other times it doesn't.
There is a write up on this in the SM that explains this valve but I have not found the section that talks about how to trouble shoot it.
I think it would fairly easy to hook up a volt meter to the ECU pin that works this. Then it would be easy to tell when it comes on. It would be the major factor for increasing the HP along with some extra GAS cause it puts more air in the engine.
