TD4 lack of power?

Hi I have a freelander TD4 (52 reg). For the last 2-3 weeks it has been playing up, some days it's fine some days it's not. The problem that I am having is that the car is struggling after around 2500 revs. Up to 2500 it's fine but acceleration after this is really slow and at 3000-3500 it just won't pick up any speed. I struggled to get to 70mph yesterday! Like I said, some days the car is fine which is really confusing me. It passed it's MOT at the weekend so not too sure what it could be?
Any advice would be greatly appreciated.

Check ALL filters...particulary fuel and air

maybe be worth checking for split pipes had the same problem with mine 2 weeks ago
turned out to be a split in the pipe from the egr/blank replaced and all is well again

oil breather filter been changed?
turbo pipes spilts will lack boost
erg sooted up i bypass mine as it adds exhaust fumes back into the inlet +10bph
inntercooler filled with gunk

Read this... http://www.landyzone.co.uk/lz/f9/td4-lack-power-70mph-fixed-77147.html