PCV system

If you start driving around fast and keep up a lot of rpm, the pressure in the crank case builds up and starts pushing oil out where ever it can. Like around the damper, breathers, valve covers, etc. And if you're trying to get all the horsepower you can, just think about the pistons trying to move down in the bore with pressure in the crank case holding it back. May not be much, but its enough to slow you down.