hi, my l322 td6 Range Rover acts as if the servo isn't holding pressure. it takes ages to build vacuum and I only get one assisted press of the brakes before they become practiacally useless. if I turn the car off it only takes a few seconds to lose vacuum. this makes me think its either a leak in the servo itself. or a broken one way valve? I assume that if I had a split vacuum line then it would still hold vacuum in the servo for a while? and would surely affect other stuff EGR etc. am I right in thinking this? does that rule out a vacuum pump issue? thanks