I know what your saying about the crankcase breather hose dumping oil into the intake system. Inside my C43 intake the oil was everywhere.

It would be reasonable to think that this oil can contribute to reduced performance as the oil can cause misfires, detonation and poor combustion effeicencey.

I replaced this hose with a longer one and routed it to an oil/air separator then back to the intake. It is good to keep the hose routed to the intake as it provides a vacuum to the crankcase which helps the rings seal and reduces oil blowby past the rings.

For the oil/air separator I used a unit for a large air compressor.

Jeff