Yes its diesel, now cry u lost
sorry to hijak your post but your problem is the same as what my car did. it is slightly better now i have replaced the stock dump valve and fitted a forge. i have also fitted a 8" cone filter, re-located horn to were origanal air box was and plumed in a dirty great induction pipe! (hence the horn move)
the throttle responce is alot better and it seems to "hold its boost" alot better. it still lags a little but vagcom threw a n75 error at me so i will be replacing that with a n75j. it also sounds awasome as you can hear turbo spooling up, and it dumps when i change gear now!!
not really solid advice you were looking for but shared info is good info! the mods seemed to help my car!
Now to many mods to list! Lots of power, torque and Leather!