Ugh.. turbo diagnostics/system

[Glyn]

Hi everyone. Hoping to get some advice about the turbo system on my car.

It's a 2005 1.9 TDi PD SE touran.

The car would run fine for a mile or two then it'd be like the turbo had stopped working. Just no power at all. Switch off and it'd be ok for a mile or so then it'd happen again. I suspected MAP sensor as something was obviously resetting when it was switched off. After a week or so the emissions workshop light came on so I asked a friend to read it for me. Plugged into reader and it came back, from what I can remember, turbo pressure or something along those lines. 

Turned out that when I took turbo off the shaft had movement in it so I replaced the full unit. The car is still the same, no power. 

Took it to a garage who says it could be one of two black boxes attached to the bulkhead? Any idea what these boxes are and how it affects the turbo?