I have to argue here because I have battled long and hard with a standalone in the past over IAT and CTS corrections.
While they may not be major issues, I am sure that having the IAT's measured pre-turbo does not lend towards an accurate mapping of air into the motor. Any type of differing airflow over the intercooler and the true IAT's (in the manifold) can be all over the place compared to the temps at the air filter.
The temperature of your TMIC will be similar to the temperature read by your engine bay IAT taken at the intake or at the throttle body. Post IC IAT readings without much air flow are also susceptible to heat soak situations and are tuned identically.
Who in their right mind would run a standalone ECU while still running a TMIC, though? If you have a big turbo, chances are your piping will restrict you from having a TMIC.
Now don't get me wrong, I am sure having it pre-turbo would work, I just don't think that it is the most accurate way to go about it. If all maps had a built in margin of error, that would be fine... but the joe blow on the street tuning his own car would likely go up to the point of detonation, and pull back a hair, basically creating an "on the edge" map that would very likely have problems of detonation if tuned for non-heatsoaked situations.