K04 GTI breaking up under boost and running lean

[JPK7]

Have an 07 Gti with a cts turbo K04 and a united Motorsports loaded k04 tune. Car started to break up under anything more than 11 psi one day and my afr gauge shows that the car seems to be running lean. Car has just had the head rebuilt, timing belt, water pump, arp headstuds and all new gaskets done to it. It is an APR HPFP in the car and is running on audi s3 injectors. I cant make sense of this issue and have no way to data log the car as of right now. It seems to me that it is something software related and not mechanical because when the car is cold it will not break up at WOT. Any idea or suggestions as to what i could check or what might be the issue would be greatly appreciated.

[pudding]

Need to data log it unfortunately, otherwise it's just guess work.  Need to see what the rail pressures are and timing pull, IATs etc etc.  In the meantime, drop the APR map down to to stock mode if possible and see if the problem persists.  11psi is about right for standard ED30 K04 map.