Honda performance

I have a 1991 cx and when I am sitting running most of the time it revs up and down up and down It seems to have fumes too. Often when I go around corners or start out from a light it will bog down and then I have to gear down to calm it and then it will pick up again. It is dangerous because people in cars behind me don't know why I'm slowing up frankly they probably think I can't drive stick. I figured it was some sort of a filter my neighbour who is a mechanic said something about trying to spray a part and if it didn't work come back my husband was told the part but now our neighbour is too too busy to help right now. Tjanks probably closr to 2oo, miles on car