Walnut blasting diesels and old turbo actuators

[Rossco196x]

I've been offered a walnut blast on my 4 pot BMD 320 D but looking for a place more local in Hampshire or Wilshire to get this done so any recommendations

Will it make a noticable difference and what should i pay for it

Also on full boost and monitoring with the bimmer App the set point is 3.2 bar but i#m only seeing 2.7 bag. given the car has done 111k thats fairly good but could it be the turbo actuators have gone a bit soft or poorly seated waste gates