Incorrect... mine worked perfect with a dump valve... never had a problem with it fitted for 4 years. The car also ran a greater BHP then cars with the Re-Circ varietyWhooshy Dump Valves rarely work on 1.8T's especially when remapped.
I'd stick to the Re-Circ variety.
When ECU gets confused it'll put you into limp mode and run like a bag of poo.
If you are referring to 100% DV then you are correct, but the ECU's are more than happy to work with dump valves, as long as you buy the correct one.looks like a GFB or Turbosmart Recirc/Atmos dumper instead) so it would recirc most of the time and only vent when on full boost (depending on how you've set it up of course)
It's a well known fact the 1.8T ECU's do not like 100% Atmos dumpers.