2004 A6 S-line 2.7 twin turbo
 

I just bought my first Audi and I have had a couple of moments where while I'm turning it seems to hesitate, revs high, then seems to "grab" and take off. This A6, drives beautifully otherwise.
It has 150 000 miles on it, but has been well cared for.
Anyone have any ideas of where to start? Or a good mechanic in the Edmonton area?
Thanks