I can say from experience that a reed spacer SAVED MY LIFE. Once. There is no performance advantage to them. They just help bigger carbs clear the clutch arm pivot. But in my blaster I have cylinder/spacer/reeds/intake. The reason they saved me was I had two screws back out of my lower reeds as I was leading. The screw heads STOPPED against the spacer and kept from sucking the reeds and screws right into the motor. If I had siezed a piston in that instance I would of gotten run into the back of by three guys running 50-55mph.