I would try what Chas has recommended, it's cheap and easily done and reversible. Heck, mine runs so much better with the potentiometer I just coiled up the wire and threw it in the passenger's floorboard. I guess I should explain that better. I bought the volume knob at Radio Shack, $3.95, solder it to about 6 feet of speaker wire on one end and put the appropriate "butt"? connectors on the other end. Ran the wire through the firewall, plugging it into the wires behind the thermostat. The adjustable knob inside with me, drove it for a month adjusting little bits at a time until it was perfect (to me).
Before I did it, it would cough spit and sputter until 2,500 RPM then pull like normal. Now it'll paint black marks out of my driveway, with a little clutch work.