[trularin]

A quick way to check all this mess is to change the carb as suggested. A new 600 to 660 will allow you to see if it is fuel delivery.

You do not say what happens after 2100 RPM. Does the car/engine run like a rapped ape? Is there clouds of black blowing out the back/sides? Is the this under load only? ( maybe you answered this question and I missed the answer ). Mr.Fixit makes a good point, this is hard to going by description alone.

Just a thought.