My only guess would be that one or both valves were leaking. I think this is the main reason why VW/Audi owners who care about performance toss the bosch in the brink ASAP.

 

My wife was complaining about her 1.8t Quattro Avant. I swapped out the Bosch DV for one of my units and she and I both swear that it was chipped. That's how bad those things are.

But, like I tell everyone, grandma's in Europe that buy VW's and Audis don't like to have their heads snap back when boost comes on, so they soften it up a bit.