My goal is to run both the factory and the aftermarket temp gauges so I can do a comparison. Seems to me the PCM gets it's info directly from the sending unit. So, if the gauge is bad, the PCM would NOT go into cylinder shut-down which it has done.

So, that leaves only two scenarios. Either the sending unit is faulty and sending incorrect readings to the gauge and the PCM or it is not faulty and I have cooling issues elsewhere.

If I were to find that the sending unit is faulty leaving it connected to the PCM would only cause it to continue to want to switch the motor into cylinder shut-down. So...IF the sending unit is bad, do you suggest I replace it?

If it is reading the temp of the metal then I presume it does NOT enter the water jacket??

So while under the motor looking for the oil pressure sending unit (can you help with that 70f100?), I started looking to see just how big (or small) the oil cooler was. I discovered two huge hoses leading over the crossmember and connecting to the lower radiator hose.

Am I to understand that my factory oil cooler is actually the engine coolant being routed into the oil filter bracket and back out?? Seems like a pretty weak idea...