Flo,
Of the top of my head it sounds like an AFM problem. Can you check it's
output voltage?  The Bentley has an outline  on Page 24.57 .

I suspect it is not producing a smooth , consistent and proportional output.

Of course, I can think of a few other possibilities. How about a general
tune up? i.e. plugs,wires, rotor,cap etc.. Also TEMPII sensor and O2 sensor.

Do you own a timing light? How does it idle? Let me know, we can go from
there.
Ken Lewis
http://neksiwel.20m.com/