Missing at high rpm after warm up



I have a late 80’s Nissan Sentra, which starts up in a snap and drives perfectly . . . . until it warms up and the automatic choke “de-chokes”.

After warm-up the idle drops like it is supposed to to around 800rpm (maybe a little slow).

It still drive OK, so long as I keep the rpm below about 2000rpm. Above that, the engine misses and the car bucks horribley.

Any guesses where to look first?