You won't get an accurate temp that low in the motor. The water is the hottest just before it leaves the thermostat. There has to be one that you could get out, there must be 4 or 5 plugs at the front of a performer intake. You can heat the intake around the plug you want to remove then let it cool before you try to remove it. If you don't let it cool you will pull the threads on the aluminum. Someone must have installed the plugs without any sealant or tape so now you have dissimilar metal corrosion. Heating will help break this corrosion, but let it cool.
Chuck