Help Please

So my mates car (PD130) has developed a strange issue this weekend. Its got a hybrid turbo with all the supporting mods, and this weekend, has started smoking when the engine is hot.

The smoke is white in colour, but stinks of diesel, and only smokes when pulling away at low revs? When in boost on WOT the smoke is grey/black, the turbo sounds fine, it isnt using any oil or water, and apparentley goes as well as it ever has.

He took it to a mechanic, who said the MAF could be playing up, so it was tested and it only peaking at 450mg/h at 3000rpm when it should be nearer 850-900? Could this cause smoking - he said due to this the car may be over fuelling causing the smoke?

Is the MAF fiddled with during mapping? I've read about some people deleting it?

Any help appreciated.

Thanks,