Low end power issue

[Brizzoluk]

Hello
I have a 2007 Passat Tdi 140, I've had it for 4 years trouble free, but a few months ago I have been having a few problems with it.
I was getting an occasional "misfire" which would only happen if i was very gently accelerating in second gear at about 2000 rpm and then i would get a misfire or a stutter/cough, if i put my foot down it would drive fine with good power all through the revs.
Recently it got a lot worse up until the point it threw up an engine fault, so i scanned it and it pointed to the maf sensor.
I took it off and cleaned it and it seemed to have fixed the problem but then it started doing it again.
I thought i would just replace it and while i was at it i took off and cleaned the egr valve, this seems to have fixed the misfire but i seem to have lost low end power, it seems to really struggle to pull until the turbo kicks in and then it accelerates as normal.
So then i blanked the egr valve to see if that would make a difference but it hasn't.

Does anyone have any ideas what could be causing this and what i could try next to sort this problem?
Thanks.