dry sump oil pump question

Even with an actual dry sump type of system you many times will still benefit from having a vaccum pump on the engine. A dry sump will pull a vacuum in the crank case but many of the times it may only pull up to about 5" of vacuum. But you also have to ensure that you have the engine sealed up so its not trying to pull a vacuum with a breather on the v/c or the dipstick tube.