Driving on the highway today, everything is normal. Suddenly the CEL began blinking and the car ran very rough for a few seconds. Then it went back to normal. Happened again an hour later.

I pulled over and checked the code. It's P0111, "Intake air temp sensor circuit -- performance / range problem."

I assume this means the stock IAT in the throttle body elbow, which is connected to the stock ECU but my car doesn't use it, because I have MS in parallel using its own IAT.

Anyone have ideas about what the real problem is / how to fix it?

Nothing useful was found in a search.