Which port on the UIM is vaccum only? I know rear has boost/ vacuum.
What about the front ports? Are these all vacuum only?

 

I believe all of the existing ports on the UIM receive both (hence the check valves used).

 

since the UIM is subject to whatever the turbos are feeding through the entire intake tract, it will be under vacuum and under boost, depending on your skinny pedal. Mahjik is 100% correct. If you wish for a sensor to see only the vacuum, then a check valve needs to be used. Just make sure the direction of airflow through the check valve is towards the UIM. this will ensure that boost does not get to said sensor.

btw, you have me curious... why do you need just vacuum?