I think Andy's comments pretty much sum it up....it will also provide additional safety if you would happen to bomb the engine.

For on track performance...well unless you have the trickiest and lightest system components...the additional weight typically offsets the power gain on the time slip.

Will you still need the vacuum pump? In the ideal conditions - no...but we are talking a ton of science and $ to get there.....technology not typically found in a bracket program