Re: Too much fuel, not enough air.
If the bike was running good then started with this "bogging" thing I doubt you're looking at a jet size problem. Something else is responsible. You say the same thing happened with the CNS carburetor and now the NT. They both ran good then started acting up.
If it was jet size the problem wouldn't just appear after a few miles.
I concur with fatdaddy in that you might have a float or float valve problem that is allowing too much fuel in the bowl. Are you using an in-line fuel filter? Possibly the float valve is not closing due to trash in the seat.
Are you using fresh gasoline? 2 cycle mix has a short 'shelf life' and should only be stored for a few weeks. Old mix won't perform as well as a fresh batch.
What plug gap are you running. .024 to .028 is a good ball park place to start.
Also keep in mind that the needle clip position only effects fuel flow at or below 3/4 throttle. Above that, up to WOT the main jet determines fuel/air mix.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"