You really do not want a Dump Valve if you have a 1.8T. It will cause your car to run rich whilst changing gear and possibly get a Check Engine Light. Some more mechanically minded people will be able to help with correct terminology and more detailed information.
Seems weird it makes no noise at all. I have a Miltek high flow cat, cat back, revo stage 1 remap and even when my plastic Bosch valve was fitted it made a slight "Whoosh" noise.
I have a Forge Split-R Hybrid valve now and can not fault it. Makes a "Whoosh" noise. Not quite as good sounding as a 100% Blow Off Valve as its split. I believe it is 60% Recirculate 40% Atmosphere so you get a kind "Whoosh" cross waste gate opening sound.