1.8 t no turbo when hot

[hertsgti]

hi
i had my mk4 gti remapped by r-tech february 09 and it has been a dream, totally transformed the drive

now  my 1.8t engine code AUM is losing most if not all its turbo function when engine temp is hot/warm

i have tried all different things like an cold air induction kit, maf clearing out throttle body

iam at a loss as to what it could be and iam slowly running out of patience
please please please help me

[will gti]

post it in the mark 4 section sum1 will reply, could it be thermostat? i dont no f all like so just a guess