Alright, on the Pre98 like yours the breather filter is that rubber tube coming from that nipple on the upper right-hand corner of the valve cover. The hose leads to the breather filter housed inside the stock airbox. It is possible to remove the stock breather assembly from the box and keep it, but you want style, so go buy some rubber tubing of the same size/diameter and one of those kool breather filters(your choice). Okay, now the purpose of the breather filter is to allow ventilation for the oil, and the filter keeps it from spewing out all over your engine bay. Answer your questions?
