ALH Boost issue and general check over

Not too familiar with these, and never seem to have much luck with any diesels I buy. Needed a small van to go on a long trip (in 3 days, as you do) and picked up an ALH engined caddy for cheap enough.

Trying to get as much sorted on it before I leave. Will give it a full service, it starts on the button, pump timing is just slightly retarded, runs ok its just very dog slow. From what I read I think it goes into limp mode. Can be ok, then hits a wall and I dread to go up a hill.

The only fault code is 17958 charge pressure deviation. P1550 35 10.

Its going on the ramp for a clutch tomorrow, and I'll try and fab something up to pressure test the system. Next I'll be cleaning the one way valve on the turbo and checking actuator movement. Any advice on what to do after this and/or a general tdi check over list would be great. EGR seems like its on near full duty cycle alot of the time for example.

I've done some logs of the map, maf and timing. I've attached the graphs, hopefully someone smarter than me can make sense of them.

I've got 2 days to get this thing running well, otherwise it'll be 1500 miles of limp mode in a hatefull van.

Cheers

Yes, I also thing you have a boost issue, but it is hard to tell from your graph since it includes several accelerations. Try to do the same flat out from 1. 2. and 3. gear. And one in 3. gear from 1200 rpm.
Your map goes up to 2500 mbar, and that could cause limp mode and reduced power. I don't know what is regulating the boost on this engine, but something there most likely causing the problem.
Your MAF seem ok at high rpm, but either the engine is modified by disconnecting the EGR or it is stuck close. It is not getting the exhaust in return and suck all the air trough the air filter and MAF. That is why it is higher than specified at low rpm, and the reason why EGR is at full duty cycle. Will not have any effect on the power dough, only reduce the sot on the intake side.