gas mileage Mechanical vs Vacuum Secondaries

Just curious how the thread got changed to double pumper tuning? I though it started out about vac vs mech secondaries. Everyone is putting some good info in here though :D I would say difference between the two is not much if the carbs were tuned the same and adjusted right. super tuning holley carb book is about the most info I have seen on these carbs. I dont think they miss anything. Lots of info and a good parts list as well.