Boostjunky

HI GUys,
Got a 2003 UK STi impreza runnin 342bhp at fly at last dyno, standard clutch went after a bit of a heavy start during a track session and started juddering then slipping as soon as boost came on. Went to my local scooby specialist and had a new flywheel and uprated organic exedy clutch kit fitted, as you can imagine the bill wasn't small. After picking it up the clutch was very heavy and still juddered, I was told it had to bed in, this didn't work put 600miles on it and it only juddered worse, it was either in or out along with constant clutch stink when pulling away or parking. There was also a constant high pitched grinding noise on acceleration and deceleration which went when you pressed the clutch. I took it back and they inspected it saying the clutch cover plate had cracked putting it down to a faulty clutch. It was replaced for free along with another flywheel as the other one had major deposits left on it. Exactly the same has happened again, clutch stink, judder and the whining grinding noise is coming back slowly, this is within 100miles. Also after both times he worked on it my cel light has come on, i've got an engine data monitor and the code is P0139 O2 sensor slow response, this will come on for a couple of days then go away again. Any help guys much appreciated.
Cheers from ross