1992 Isuzu P'up

My 2.3 ltr engine is revving high and it just recently started doing this. I
tried adjusting the throttle rest adjustment screw but it did nothing for
it. I should note that the carburetor has had a moderate miss to it for
some time now. I took the filter element and housing off and it still revs
high. I checked for proper connections of all vaccum lines. I have an
aftermarket air conditioner that was installed in 2000. The engine has
111,000 miles on it and does not smoke.

Can anyone offer some advice.

Thanks,

Ray