Hey Lille-bror...
Hmmm...I've never had mid range problems with any of my TT .46's? Got 2 of them now, and had 2 more previously, that I traded stuff for...
Just thinking here...perhaps your low speed needle is loose/leaking/not set quite right?

I also have an MVVS .49 (8 cc ) and the carb neck is 13 mm
I don't recall right now, but is the carb neck of the TT .46 also 13 mm?

Perhaps Dar, or Pe or Jaka can confirm if that pic of yours is an MVVS carb? It looks a lot like the carb on my .49 but not quite exactly.