Where to mount?
 

roots blown, efi motor. Do I mount the Intake Air Temp sensor in the flame arrester or should I drill and tap a hole in the intake below the intercooler?

My thought is the second choice but I thought I would get opinions before breaking out the drill.

In the intake below the intercooler. If you put it in the flame arrestor, you take the blower and intercooler out of the equation. A bigger blower or bigger intercooler will have less air temp than a small blower or smaller or less efficient intercooler.(assuming they both have the same boost) If you put the sensor in the flame arrestor, the examples above would read the same temp. while the temp in the intake would be much different. You want to know what the engine is seeing. Hope this helps,
Eddie.