01 Volvo D12 pre egr boosting only 7psi

hello
i have 01 volvo 670 with d12 engine... i have this truck for over a year now and recently i changed company i work for , and i realize something is wrong... before i was pulling most of the time empty trailers but now heavy reffers...
First thing i realize it was fuel drop from 8's ro low 5s or high 4s mpg and boost its showwing usally 7-8 psi with full throttle... sometimes it go's to 15psi but with 1800rpms or higher....
last year i did overhaul (turbo, head, sensors, all new front engine with new gears , etc)
boost sensor was also replaiced year ago.
Engine starts every time w/o any problems, its nice and clean, no air leaks ... any ideas???

 

yes, i mean that ... my mechanic also check last night turbo.... everything looks good.... i just purchase another boost sensor... let see if thats can help....

 

boost sensor is replaiced... still the same :/

 

whats the EPG?
no codes for injectors, no smoke going from tail pipe, caps and harness changed last year.

 

i called mechanic and he said its working fine... i'm not sure how he check this but thats what he said...
he said probably its a turbo but there is now oil inside the turbo, no play on bearing... looks really good but he said there is nothing alse...
last year i did overhaul and i change front gears... maybe there is some problem?? bad timimg? but if there was something off, engine will work bad? i mean something like hard starting , or smoke going from the tailpipe??
i didnt say before but i have straight pipe... no muffler. i hope thats not the issue