On long trips, the area under the front passenger seat of our '95 965 radiates a lot of heat. The seat bracket gets too hot to touch. Has anyone else had this problem?

I assume that it is the exhaust system that is causing this. There does appear to be a heat shield in place, and the pipe is suspended below it. Perhaps unrelated (or not) we keep getting an O2 sensor code on long trips. The check engine light comes on after ~150 miles of continuous highway driving when going up a long hill. I have replaced the O2 sensor and cleaned the ground connections near the fuel rail. The engine ground is clean and tight as is the battery to frame connection. I would like to test the O2 sensor output, but how do I connect my voltmeter to it without unplugging the connector?

Thanks again,
Steve in NC

'86 745 with 200K
'95 965 with 96K