The Pros and Cons of Racing Vacuum Pumps
having worked with a friend who used to drag race his mustang with a 460 he used to go on and on about how he loved his vaccum pump.
long story short for him it controlled oil leaks due to blow by, and gave him 32 hp. the theory behind it is if you have more than 4 but less than 15inhg it will cause the rings to seal better.
maybe a cheap way to pick up a few mpg