just seen a pic of an erst engine and in the pipe there was a t piece with another pipe coming of it,what i was wondering was where would the other pipe go to as on my erst there isnt a pipe like this it just goes from the actuator to the compressor housing

 

The only thing which ive seen done is blank of the compressor housing pipe and run the actuator pipe straight up to just in front of the throttle body. By doing this the waste gate will stay shut until the desired boost is built up to the throttle body and not just in the compressor housing.

Ideal when running a big cooler as you usually lose boost because of the amount of air needed to fill the cooler and pipes etc.

Apart from this I have seen what you described and it was connected to the dump valve vacum pipe as a way of keeping it shut on a diaphram dump valve?!?! Couldnt understand it personally but hey someone might explain!!