Sorry - fell off a ladder a couple of weeks ago and have not been online.
I refer back to my first post regarding this issue suggesting that the fuel lines etc. may be blocked?
If there was debris in your tank it can only have gone one way - into your fuel lines, pump, filter and injectors.
You now have a considerable task in order to get the bike running correctly again which involves stripping everything down from the outlet on the tank to the engine manifolds.
Regretably this is a very time consuming task but it will obviously clear up your issues. I am surprised that mechanic did not do this or suggest that it needed doing.
Depending on the type / amount of debris it could well be that the injectors will need replacing.
Not easy to do but can be done with a little patience and methodical approach.