those breather caps are garbage. my system is completely closed. valve cover - pcv - carb. i have no breather what so ever and this set up works flawlessly . some use a breather on the opposite side of the engine of the pcv. if your carb is connected to a pcv breather with holes in it , your are sucking air and not crankcase pressure. there is a valve in the PCV that vacuum from the carb pulls open to vent. pcv= pressure control valve . your breather needs to be tossed in the garbage and the correct pcv installed.