Well I went ahead and plumbed into my external additional brake vacuum reservoir with no ill effects so far.
For the maps, my 1.8T had the idle functionality disabled (SVDLDUVS all set to 1, which can never be true with a pre throttle body MAP sensor). I have re-enabled it by copying it from one the other files (1.11 at 600rpm and rising to 1.38 by 25000 RPM). This should be more beneficial on my setup, where the DVs are located right before the throttle plate so all the intake including turbo and IC can be by passed under light load.

I have also increased GWPLDU to about 6% to prevent the DVs opening on small throttle fluctuations.

Boost spikes completely gone and I confirmed that the DVs are open during cruise.

Hi,

I´ve done the exact same thing with the N249 because of a terrible boost spike after I release the thottle.
Now I see next challange... getting rid of this turbo flutter I have (you can see from PrtSc). Btw dv is splitter,
works well no mil etc...
I was thinking to modify the splitter valve, because I think there are too small holes inside the valve
for releasing all the pressure (between the pressure and intake side).
Could it work? or is it more likely software issue?

PS: running GT2871R (testing and learning step by step).

i assume GWPLDU is a map. how did you define it? what are the axes?