There's no problem with the downshift. I can duplicate the problem even when shifting first to 2, which causes the car to shift to first gear, before taking off.

I know the car is noticeably peppier without the A/C on, but this is a clear case of "some times it goes, most times it don't"

That's the problem with disconnecting the throttle pedal from the butterfly. At least with a mechanical connection, I know that X amount of pedal gives me Y amount of throttle opening.

With this setup, I have no way of knowing what a given application of throttle gives me at the actuator - the computer decides what's right, and hopefully the actuator does as told.

I'm just wondering if there's a way to test the actuator to see if there are issues internally, other than pulling trouble codes.