Ok still having problems (08 Passat 170 sport DPF) PD

Having changed the MAF Sensor (new on from VW) the car was fine for about a week, now it's back to same old lumpy, sluggishness, power loss, Turbo kicks in intermittently, low 34MPG, car is constantly doing Regeneration of the DPF, (had the DPF light on 3 times in a week) over the weekend, the DPF light came on, took it for a spin on the M1, that cleared, came home, after an 1hr i started the car, and withing 2 mins it started the regen process, there was loads of smoke coming out the back..
The regen which lasted 20mins.. then about 1 hr later it started again.. ***!!!!

Last week, the local VW mechanic checked everything on the car top to bottom, pipe leaks, sensors and the DPF, only thing he noticed was the air flow would drop by 20% after 5 mins, so installed the new MAF sensor..

I changed the fuel filter (which was totaly black) recently, only changed about 5K miles ago.. I emptied the contents of the housing in to a bottle, left it for a day or two, noticed that there was oil in the fuel .. I also get a loud "droning" noise from the rear of the car nearly every day, not the regen sound, it dissaoears for a seconf or two when i blip the accelarator pedel and back again... leave it idleing for 5 mins then something clicks and it stops...

wierd thing is it drives fine when you start the car, u can hear the turbo sound when accelerating, but gradualy after 5 mins of driving, i don't hear it and the car starts to struggle.. loads of Misfire.. starts jerking too...

it's a never ending story.....