rcprato - I tested the waste gate and it seemed tight, also no rattling on my end as well. Performed a boost leak test and didn't find anything. Do you know what that sensor is for? Temp?

misiak - Keep us posted on what you find!

This surging sensation seems almost too similar to common B7 TC failures, although I'd like to believe this is not a transmission issue. For myself, its more common in D, although can still feel it in S & M under the right conditions.