Adamkiwi -
it could be any number of the excellent suggestions already posted, but what about your local temps?
how cold was it when you were driving?
I've heard on this forum that the MS3 cuts boost in the cold.
Not sure how much but if it cuts more boost than would normally be increased to do the intake of colder, denser air, then that would explain it too.
Here in Indy, I've noticed the car feel very un-exciting at 19F at WOT in 1st and 2nd and then at 45F feel like the usual beast needing some throttle feathering...
It's quirky in turns and at lower temps...