Volvo 850 TDI turbo almost not working

[Charlyf]

Problem is that turbo on TDI gives some pressure only after 3500rpm, at full throttle pressure is around 165kPa according to ECU live data.
Air flow at idle is twice expected value at idle an almost not changing bellow 3500rpm where it starts to rise and is almost as expected.
All measurements are taken without load not driving.
Begin of problem is not known because it was bought already in this state.
Car was driven with this problem unsolved for two years and live data readout is not changed after all this time.
Fuel consumption is very low, around 6.2liter/100km, previous identical car with working turbo had around 7 percent more consumption.

To this time following repairs/tests had been done:
1)installed ECU from previous car - no change
2)installed MAF from previous car - no change
3)removed waste-gate from turbine and checked, piston moves and spring has the same strength as part from other car
4)control valve really switches iar flow with 90% pattern as ECU reports
5)vacuum tubes are checked and connected according info from VADIS
6)with vacuum cleaner checked air tubing and inter-cooler - no blockage or serious leeks
7)cleaned intake manifold and inlet openings (as possible), blocked EGR after this with plate in place of gasket
8)cleaned pressure sensor tube and checked sensor
9)Turbine axle spins freely by hand and has play 3 times smaller than turbine from previous car
10)with removed exhaust at idle turbine spins like a computer fan (around 1000-2000rpm I think)
11)with removed air filter nothing changes

Questions:
a) why air flow is twice the expected value on idle according live data
b) why turbine is not giving any pressure bellow 3500rpm

Last test possible is to put in turbine from previous car, but I'm not happy with it because of high wear on that part.
Live data at idle are attached.
What You suggest, is this likely to be turbine fault and what can be wrong with it?

[scot850]

I hope there may be one of our European members that can help with this. Few if any of us in North America have diesel experience as they haven't been sold by Volvo here since the 240 in early 80's.

Neil.