outburst of oil from the filler cap
In earlier models of the Rx8, the oil breathing system design was not that good. One of the main issues was that under heavy load, oil would go out of the tube under the oil filler cap that goes into the intake and leak inside the air filter box.
To solve this issue, you can install an oil catch can. The catch can will catch the oil that comes from the engine and deliver just air into the intake, like it should've done in the first place.
Click HERE for the oil catch can install video.