In that case I'd say it's either a sensor with a bad contact pin (this would cause it to not send enough milli amps to ecu to be able to read signal properly, is there a limp mode in the ecu), by removing and reinstalling have you bumped a turbo sensor.
Its certainly a strange one in that it did it to both ipd ecu and stock one, that would suggest a sensor that sends info to ecu.
I got my OBD2 checked yday at reliable volvo dealer that services a couple of 850Rs and they said it didn't have any faults and all they did was turn service light off.
Yet two weeks ago tracs light came on suddenly, went out after I parked the car but that triangle warning light came on when I restarted car that says there was a electronic issue in engine bay, I reset it by disconnecting battery earth clamp over night and it's been fine ever since as supported by ydays OBD check at dealer, old cars is all I can put it down to with a poor pin to socket connection.
Its a tricky one