I have the car booked in with AmD on Tuesday afternoon now. We are going to:
(1) Take the car out for a drive to demonstrate the problem
(2) Perform some diagnostic logging whilst replicating the issue
(3) Try a Revo Stage2 map
(4) Try some different fuel mixture, timing + boost settings with the Revo
(5) Inspect the spark plugs
Hopefully we will at least get closer to an answer tomorrow...