R-Tech are very well worth considering. We took our GTi 1.8T there last Thursday and the service was first class. The car was thoroughly checked over for both software and hardware faults to begin with. The car was custom mapped with rolling road before and after the map was applied. My son took it out for a quick spin (I have just had a foot operation so not supposed to drive at the moment) The smile on his face told the whole story
On the way home he was in third gear with a damp road. He put his foot down and as the car came onto boost the engine revs rose and there was a sort of whirring noise but it did not push me back in the seat. I thought that the clutch was slipping as it could not cope with the increased torque. But I was wrong, the clutch was fine and the whirring noise was the wheels spinning on the damp road!!!! It never used to do that in 3rd gear.
No flat spots, just lots of power compared to standard. I should have had this done years ago as I have owned the car since new in 1998.
Peter