I had the same problem. Busted idle up p.s. Vacuum valve. My truck would puff smoke when I drove over rough stuff, the engine oil was overfull. I was losing fluid like crazy but no leak. I checked the idle up valve by adding leak detector dye. I use a black light to check the vacuum lines that run into the side of the intake, they glowed.

 

I had that problem but on mine the ABS unit was leaking and it was all just "slipstreaming" away around the frame and axle [which is also under the PS pump] so tracking down the leak was a bear. It was also leaking brake fluid so we just disconnected the whole thing from everything.