Was driving my 01 Jetta ALH and the brake operation was fine and then randomly in my drive they got extremely stiff. I have replaced the line that goes from the vacuum pump to the brake booster and although mine was not in the best of shape it did not fix my problem. I took the line off the pump and started my car and held my thumb over to make sure there was suction. There is suction but it is not really hard by any means, I don't know how many inches it's supposed to suck. The brakes will feel normal for one pump after a while down the highway, I'm assuming its having enough time to build up pressure. Is my pump or booster toast? Will be getting a lot more in depth in my diagnosis this weekend when I find a heated garage cause playing under the hood outside is not fun in Michigan in January lol.