This is just thinking out loud Norm, but you know how some of the decomp nozzles have the little brass restrictor and others don't? I think it was to prevent a backfire causing the valve to smash into the 'ramp' in the cylinder and break the stem.
In theory there would be a slight difference in how the vacuum is delivered to the diaphragm - slower or faster
Don't know if the difference would be appreciable though
