Finally someone else has the same problem as me!
On my way home, I go over some big crests and in to some dips. My GTD also cuts the power. I left it in to VW to get looked at as I though it was a fault. I would be driving quite fast and all of a sudden it is like there is a limiter put on. VW said the car feels too light over the crest or feels to much load in the dip then cuts the power. It is like dabbing the brake and the car cutting the power. I was told that it isn't the actual traction control kicking in which explains why the light doesn't come on. I was told there are some other sensors that look after this.
It seems we are stuck with this! It could catch you out when racing if someone is close behind you then the power cuts, suddenly the car behind is now in your back bumper!