If the same chap who remapped your car takes two weeks and still cannot say for certain that the issue is ECU related then IMO it's time to take it elsewhere.
You need to ask these questions:
1) Did he write the map and does he actually have experience in doing this.
2) Has he actually double checked all of the parameters that he has changed or altered on the map.
3) Has he used the correct information about the turbo with regards to writing the map.
I am no expert (Far from it) and can only go on things that I have experienced on my own turbocharged car. I recently had a massive upgrade in turbo size and had an issue with power delivery that took all of 2 days to discover and rectify.
There are some truly great guys on here who are extremely knowledgeable on turbo engines; Claymore, sleeper, old-git, Jarrus to name but a few, hopefully they or others will be able to shed some light on this problem for you.