[b3lha]

Measure the voltage of the white wire at pin b8 of the TCU. This is the wire from the TPS to the TCU. With the throttle fully closed it should be 4.0 to 4.8 volts. At WOT, it should be somewhere between 0.7 and 1.7 volts. Go for a drive with the voltmeter connected and see what the voltage is when your spurious power mode occurs.

If power mode activates while the voltage is >1.7 volts then the TCU is at fault, otherwise the TCU is just doing what it is told.