Inconsistent turbo spooling

[P156KWJ]

Unusual behaviour from the turbo on my 1.9D, it's as though it's constantly trying to do something (not making any unusual noise, just doing it when it shouldn't, the usual sort of faint noise you'd expect if you come off the accelerator to drop the clutch at higher revs. It seems to happen mainly in 2nd if you're for example in a moving queue in city traffic, giving slightly inconsistent and rougher acceleration than normal.

Changed the MAF sensor (twice, genuine ones) and it's still the same, if you unplug the sensor the issue goes but then the car just drives as though it has no MAF (obviously) and that presents other minor issues.

It's still perfectly driveable and if you are driving more enthusiastically shall we say it still goes like stink, but for normal driving it's becoming more noticeable and wondered if it's a sign of something more sinister further down the line, or whether it could be something reasonably simple like another sensor at fault.

Sorry I can't describe it much better than this, thanks in advance!

[P156KWJ]

May have answered my own question as work's Snap On ethos gives me a code of 1804 which is a boost pressure sensor fault.