Reply to "Stumble during acceleration"

Bogging, carb backfires or stumbles are most often due to lean outs. Many areas to look at with tuning a carb. I only know Holley's but I think demons are similiar. You might need a different vac secondary spring that opens the secondaries sooner. A larger jet might help as well. Lastly a larger squirter would allow more enrichment in the transition from idle to accceleration. Best to get a carb tuning book as they provide graphs and pointers on where to look first and what size to use. Look at jet sizes, squirter sizes and different vac springs. It is a black art and requires some trial and error.

It helps to make sure the spark is strong and that the spark plug gaps are to spec. Elminating spark issues allows you to concentrate on fuel problems.

Lastpushbutton, my experience with MSD's is that when the fail, they fail. No spark what so ever. A dropoff in a specific RPM band does not seem reasonable, check caps/rotors, wires and plugs if the are good and the wires ohm out then fiddle with the carb.