While I don't have much to offer to this thread, perhaps this one detail might be of interest. In working with the '97 PCM and I believe all those from '94 up, low power mode is entered by resetting the Power Monitor IC (PMIC). The circuit uses too much current to just stop the CPU. When the PCM wants low power mode it goes into a tight loop: bra *
After the watchdog/cop time out the PMIC doesn't power until it sees ignition voltage.

Any mod to the car that asserts leakage voltage on to the ignition: even a very short pulse will turn on my pcm.

Hope this is of some use.
-Tom