00 Subaru Outback hiccup at cruise

My 2000 Outback 2.5l hiccups at cruise. Usually it is worst at highway speeds, but can happen at any speed if cruising at a constant speed. It will accelerate fine at any speed and idles fine as well. 95% of the time the CEL does not come on, but the other 5% of the time the light comes on as well as the AT Oil Temp light(auto trans) and it shifts hard and stays in gear until I restart the car. It has pulled a P0122 code which is the Throttle position sensor circuit low input a few times thus I have replaced the TPS twice with absolutely no change? Any ideas? I thought something with the ECU trying to lean out the mixture at cruise, but leaning to much? Please Please help this has stumped everyone so far! Thanks! Sean

Is the engine misfiring or is it something in the transmission? A misfire will turn on the CEL and set a code, but I don’t know why it would also turn on the AT oil temp light.

The transmission fluid is clean and at the correct level, isn’t it?

The TPS code may be due to a wire connection problem rather than the sensor itself being bad. I would check all the connections between the sensor and the ECU for that circuit to see if there is any problem.