Error code: 6805 boost pressure control, control deviation positive

[kznforvolvo]

Good day Everyone

I am having a problem since day 1 with 2004 volvo xc90 D5 2.4TD

Car kept going to limp mode and loss of power - specially when aircon was also turned on (town and highway did not matter)
I have taken my car to diesel mechanic and he has done the following:

Replaced the solenoid on the engine (original volvo), send turbo away to be repaired, checked all air lines. The intercooler was newly replaced before, also the engine mount. EGR was also cleaned.

Once i got it back it was allot better, driving in town i have no issues, but now when i drive long distance exceeding 30km distance etc engine light comes up. it will light up, and after 20 seconds it goes away. this will continue for a while until the light remains and i then feel the car goes into limp mode. Funny thing is if i am above 80km/h i can accelerate and after a while the warning light goes away and i feel the regain of power.
if i am below 80km/h it loses total power and eventually i need to stop and turn off and turn back on specially in town.


We are stuck. Any ideas?