Thanks for all the help guys
I've looked/listened for leeks at idle but non are obvious.
I do have a vacume guage fitted so if i new what vacume my car is supposed to have at idle i could test it that way.
I pulled apart my air flow sensor and re soldered the all the "problem" spots but it didn't make any difference.
I tried reving the car in park and it revs happily to 4-5k(no point thrashing it) which it wont do under load as it generates boost well before then.
This leads me to agree that its prob a boost leek.
So i guess now i'll have a look around the forums and see if i can find a good way to test for boost leek.