cracked manifold replaced - need more pointers on what to check next re low boost

[omodos]

Righto its me again to nag you all (not got a 3.0d sport so post sort of directed at diesel boys i guess) , morning, okee got my cracked stainless steel manifold replaced friday....symptoms were basically puff of smoke on cold start days in engine bay(not out of the exhausts) smokle was just sort of below where wiper water tank is...plus sooting up of the immediate area...now coupled with this but seems was not the reason for issue is that recently i notice low end boost on the turbo was gone....

Was hoping new manifold would improve this (air filter also changed) alas nope at about 2000rpm is when the turbo will kick in whereas prior to this was @lower revs...so issue must lie elsewhere, read heaps of posts and am getting lost in translation...what are the best steps to follow(or pint a mechanic in without pissing em off) so far this is what I have read been done
1. the piping on either end of the vacum accumulator have been changed by mechanic (one person on board said start engine pull off both pipes and if you hear a hissing noise means your vacum piping is all ok? true or not no idea?)

2. I pulled the vacum pipe (black and blue tube) off the EGR and plugged this pipe as a test made nooo difference (this was a suggested test on one post to eliminate EGR as issue) i could also make out now that engine was sparkling clean that that same pipe was connected to the other end in the turbo area and not hanging off in anyway

3.And then i went onto read about vacum actuator vacum soleniod etc

4. piping on off intercooler etc (that i am sure mechanic must have checked as part of taking off manifold)

Am at a bit of loss here as got trust issues and not sure handing it over to any mechanic will help...mindyou guy who did manifold did mention a solenoid at back of engine maybe cause for low rev rpms, and am sure if turbo was duff he would have mentioned it during the manifold replace.......

Could it be a case that the soot dished out of the cracked manifold fouled the filter on the vacum actuator/solenoid inhibiting its action until high revs reached? and its a case of it needing a clean as wpoll mentioned in one most and included a you tube vid of this?

Dunno am at a real loss, car ain't broke and for sure the manifold issue sorted but it just aint whooshing away when i hit the pedal as it used to do and it hurts! I could hear the turbo wheeze so to speak from day 1 at much lower revs since 2008 when i got her, and this was of course accompanied by the power

Any pointers to a novice much appreciated..and more so pointers that I could try myself...cheers