Thanks Paul. Makes sense and that's what I was thinking in post #12 above.
The thing that confused me was "the IACV sits at the back of the UIM and is part of the return feed system that recirculates used bad air contaminated with oil vapour" since I don't see it as part of that subsystem. Even if under high manifold pressure it may actually act that way.
Apologies if I read you wrong mate.
I was tired and probably didn't put it across properly, plus that's the 5th thread I think I have explained it in so its getting a little tedious