Is my dealer correct in saying"any" loss of pressure due to TBB, DVs would result in a "Check Engine" light?

TBB "flapping" where it flaps open and leads to surging doesn't always produce a check engine light. BPV/DV problems I don't think ever cause a check engine light. Could be wrong about that, but it is quite possible to have BPV problems and no light.

I don't recall exactly the case, but there are also <b>LOTS</b> of S4 drivers who've blown the TBB - to the tune of 1.5"+ tears - with NO DTCs whatsoever.

Search archives for "TBB" and you'll find a ton of info.