Have you pulled the plugs to do a visual… are you running too rich? Your plugs should be a dark tan color. If you are running too rich, you'll have dark brown or black looking residue. Run your car around the track at the 5,000 to 6,000 rpm range, clutch and kill the motor. Pull a couple of plugs and see what you've got. You can get a pretty good reading on your fuel mixture this way.

Dan J