300tdi power problem

Over the past few months ive noticed a problem with my TDI, it revs cleanly upto say 2100rpm, at that point its like hitting a wall, the revs slow right down and feel strangled almost and to make progress you have to rev the nuts off it.

I know this isnt right because occasionally its different, as soon as the revs hit 1800ish it will rev smoothly all the way past 3000rpm with plenty of grunt.

I have checked the turbo hoses, all seem ok.

I have a suspicion its down to either the lift pump or the wastegate,

again it drives ok at low revs and will move along if you really wind it up but its just frustrating to have it running so well whenever it feels like.

any ideas?
thanks

Sounds like the air intake system
check the following
Air filters
all air hoses splits/crack/loose clamps
Dirty internals of the innercooler
Turbo hoses before and after turbo split/cracked/loose clamps
And breather from motor EGR hose??? pluged/ restricted

well the egr is blanked and the hose plugged but the rest I shall check out, thanks