I've only installed a few smoke systems and none of those recently, but all of them had smoke in the cockpit. Not sure you can stop it completely. But yeah, opening the cabin vents should help. Side note, it's always interesting to watch the smoke system work on the ground with the cowl off. Smoke comes out of all the slip joints and ball joints, even downstream of wherever the oil is injected. Shows us there's a lot of back and forth flow in even a free-flowing, healthy exhaust system.