I see what your saying. Sort of. You are saying the correct distributor accommodates the timing mechanically at idle and does not benefit from MV? Some of the old mopars only have MV ports on the carbs. I still think tuning a performance street engine you tune the mech adv to the most power and response then run MVA and set the vacuum to below ping under load. This has always worked best for me. But I will experiment when it warms up since I can taylor both mech and V adv curves easily.