Knowlegeable D3 mechanic/garage needed?

[centurion]

afternoon,

I have this very weird issue with my car that I have taken to several reputable places to date and they haven't been in position to diagnose or provide a 'fix'... hence was wondering if this is something you could advise on and recommend someone who actually knows D3 A8's and especially 4.2TDI motor?

Issue:
cold - working fine;
temp slightly up: starts stuttering/juddering at low revs
nominal working temp.: all fine again

to date I have replaced MAF's, air filters with genuine Audi, checked VCDS several times to no avail.
MAF's were replaced due to similar symptoms I had on an A6 2.7T when it failed.

something to note that A8 worked brilliantly when MAF's were off [Check Engine light came on but there were no juddering at any point and I have driven it for a week like that]. Thinking MAF's were erroneous I ordered new Denso parts (x2)- replaced them and the issue reappeared so to speak. I also ran several scans on VCDS w/o anything tangible that could point to the malfunction.

and to add... I had driven the car around Europe like this [with 'an issue'] there were no problems having covered 4.5k miles apart from what I described earlier. I must say that I did 155mph on several occasions and having brushed off several 911's en route I don't think that car has a major problem... it must be something electrical that controls fuel-to-air mix etc.

I'm not perfectionist by any means but this had been bugging me and I'd really appreciate need someone who understands these beasts to diagnose the fault hence the pleas for assistance ?

any advise would be appreciated... thanks.