the throttle body should be in the region of 25-45 degrees really as if carge temps exceed that then your intercooler isnt really up to the job i wouldnt think they can ice up,

im not 100% sure here, but on the wrc escos plenum they run a anti lag valve in the side of the plenum just where the temp sensor normally is so maybe something to do with that, could be way off,

i will ask the old chap tomorrow he has one of the grp a throttle bodies at work im sure he'll know why

jim