I'm removing the valve cover to start the valve adjustment on my M30 and have found that the breather hose seems to consist of hard plastic. it is held onto the valve cover with the usual metal screw clamp. when i went to pry it off the valve cover a bit the hose snapped off a bit at the base. is it supposed to be hard like this or is it because it is just so old? can I replace it with some regular rubber hose? thanks.