I'm loosing brake assist now and then. This last time was when it was raining. I've replaced the main vacuum hose between the manifold and the booster (no clamps are currently on the hose and I haven't applied vaseline to the check valve yet). I've tried spraying starting fluid around vacuum areas, but get no idle surge -even when I pull a vacuum hose and spray into the nozzle! Do I have a major vacuum leak or is my booster or check valve at fault? I don't mind driving it this way as it happens only now and then, but my wife is not impressed.

-Thanks in advance