You have to get the engine sealed, TIGHT.
@gregsdart was dealing with rear crank seal issues, but I forget how much vacuum he is pulling.
If you don’t run thin rings, which is 1mm or less, back cut them and use gas ports, you won’t get the biggest power increase from pan vacuum.
And, and this is a big AND, the more vacuum you pull, the more it changes the surface finish on the cylinder walls, including cross hatch angle. So you have to be understanding of that.
There is more to crank case vacuum than just bolting on a pump. You need to consider everything it affects. There is power in it for sure.
