Good information in this thread as well,
LINK.
So I have the 3.45 diff gear set and it worked fine with the OE DCT tune. I then tried one of the revised aftermarket DCT tunes (Alpine) and noticed the rev matching was a bit off. This may have had something to do with my engine tune though, Dinan Stage II, not sure, but I went back to the OE DCT tune for awhile and then recently flashed the OE GTS DCT tune and that works flawlessly.
I ran in S6 this last weekend at COTA, lightning fast shifts and no issues.