Technical Multipla problem help needed

[skylinenuttergtr]

My Multipla JTD engine management light comes on after ive floored it through a couple of gears the goes on limp home mode(no boost). I plugged it in and it came up with crank sensor(inttermitent) which I changed and map sensor(boost sensor). It said low boost. I took it out and it was crusted with oily ****e so I assumed it was blocked. I cleaned it but still the same so I replaced it but still the same although a little better as its not always on shut down. I am thinking it could be
1 a leaking boost pipe causing low pressure and the turbo overboosting causing the oily ****e to leak past the seals in the turbo blocking the sensor.
2 A bad earth to the ECU as it had a smack and I took the wiring loom out of the way for painting then replaced it. Also wondering if sensor isnt getting live feed properly from ECU.
This is the 1st diesel turbo Ive played with so is it normal for so much oily crap to be in the inlet tract?? Any thoughts anyone? Want to chip it and add 60bhp asap(watch it go bang!!)