ideally you don't want to be sucking in oil and harmful vapors either. That can cause detonation, fouled plugs, decrease intercooler efficiency, loss of power, and dirty pipes. According to Enthalpy (Scott) anyone with the boost up should delete the intake vacuum line on the oil catch. It is for stock cars only. Anyone with more than 350 hp should cap the crank case line. Any SR with 400+ should have a breather setup like mine. You guys with blow by going back into the intake on modified engines are killing yourselves.