Hello,
From what I read think your 3MA is running like it should, I know that sounds doubtful with the described symptoms.
The problem now these days is that the 3MA is lift on a platform they not belong
Terms as ultra rare, unique, special, only 500 made, etc are words many times used with a sell of a 3MA.
Prices are sky high, and disappointment is something that lurks around the corner
From a technical point a few, they are great.
Carbs at the frond, exhaust as straight as possible at the back a real race replica from the TZ racer. (from memory the TZ's at around 88)
But from a road riding point a few they are not that good.
The fueling problem was and still is,
the biggest problem the 3MA has.
You have to be a real 3MA enthousiast to live with this and work your way around it when driving
What you can do with your bike to see if its running like it should, try the following.
1) When you use the choke its only use for starting the bike, when it runs try to close it as soon as possible (it will fill up your crankcase in no time)
2) Ones its running keep it running on throttle (not on choke) let it slowly climb in RPM and not stop at 5000rpm let it climb till +/-8000rpm or higher.
3) when you can hit 8000rpm or higher this will be good enough to ride it trough the street
4) Warning you will not make friends when you ride through the street, as it will smoke like nothing else, but try in second gear to let it accelerate to 8000rpm
5) ones that is going all right you can let it pull till +/-11.0000rpm (most off the fuel in the crank cases will be gone then) it will feal crisp again.
6) check the throttle response now if its like it should, ones the crank cases s clean it should kick out those rpm's without any problem
Same is for riding a 3MA (with a fixed airjet)
1) Don't drive to long behind a slow riding car, let your bike slow down more shift down and accelerate so your clear out the crank cases
2) try not to ride to long in low rpm's (it will fill up again)
Its a play bike, ride it in the higher RPM's and she will go like a dream
Good luck