Your Mx5 isn't running as cleanly as you thought, and this air-oil separator from Moroso is what you need to clean it up. The factory designed the engine to vent excess vapours and oil back into the intake manifold, causing oil deposits that gunk up the intake and the valves, and crankcase vapours which could cause detonation. Plumbing this air-oil separator into the PCV system captures the oil and moisture and contains it in this great looking billet canister.