Originally Posted by the suicidal eggroll
As long as it's after the intercooler and isn't in a position that's prone to heat soak, it doesn't really matter. I would ONLY put it in the manifold if you're running phenolic spacers to keep heat soak down.
I have fairly thick phenolic spacers and put it in my manifold specifically to test this and I wouldn't recommend it again. The temperature readings aren't insanely high, but still elevated. At least in my mounting location (the plenum) the update rate was fairly poor, I would only see about a 6* rise at 20 psi from 3400 rpm (where it hit 20 psi) to 8500. I would expect more than that on an HTA Green and a longer pull.
Most of the time the sensor was reading 30-40* over ambient and during driving was a fairly consistent 20* over ambient.