97 Jeep Cherokee freak error

Hi,
I have a problem with a 97 inline 6cyl Jeep Cherokee sport: the check engine
light came on and the code with it is PO123 "TPS input circuit A high ". So
I replaced the TPS: no change. I measured all voltages: seems fine. I
replaced the engine control unit: no change. I exchange the throttle body
with all sensors (I stripped a thread when I first tried to take the TPS
off): no change.
It is not a fake error because the performance is really bad. The car stalls
when you aproach a stop sign, the idle goes down to 300rev when I get of the
throttle. And when I first start the car I need 3 times to start it.
I also checked the wires to the ECU and they seem fine.
Any thoughts if I am mislead by the error message of the OBD?
Thanks in advance

Jo