Can some1 help me please :)

[Mk4-mel-x]

Hey I'm new to the site so I'm abit rusty ATM ! I have just brought my mk 4 gti 1.8 T with a stage 3 map on running at 250 bhp. Basically it's not boosting right when you put your foot down she's spluttering the power just ain't there  my mate has been looking at it all day yesterday and can't find the problem any1 have any ideas?! Thanks 

[Dalo Harkin]

Check the basics

MAF (gets dirty if using anything other than a dry filter)
Plugs - in decent condition?
Coil packs - you know one is shot when it sounds like a retarded Subaru  (best description ever whoever came up with it) you can also check them one by one by doing this:-
Start the engine, remove the wiring harness via the little clip on each one, if the engine note drops its fine if not its buggered