The G187/G188 sensors are located within the throttle body, quite a common fault on the Tfsi for the throttle body to become coked up and stick, you could try either cleaning the throttle body, throttle body reset (requires vcds) or go for a new or known good replacement unit,
There was also a TSB on the wiring harness/plugs relating to the throttle body iirc, I'll have a look if I still have it somewhere