is it true that if you add a pump that will pull vacuum through an engine's valve cover, and essentially from under the piston, can add horse power? my friend is an old hot rodder, he has a 528 bb chevy that has an angle cut 3/8 inch pipe that goes from his headers (collector) to his valve covers. he was saying something about the piston rings being more efficient whe the oil side is under vacuum. anyone know about any truths to this? will it work on a 4 cylinder engine?