Having an intermittent rough idle. Each time rough idle starts I lose power brakes . When I remove the Brake Booster Vac line...Engine runs smoothly...Back to running rough if I place my thumb over vac line....Also have a constant hissing noise coming from area of the brake pedal when engaged....Any tips???

 

Seems like a leaky vac hose there. You will probably need to replace the vac line. If you're not sure on which line to replace, try spraying some brake cleaner around the hissing sound and if the engine revs higher then you have found your leak.

Wow, I think I read your post completly backwards. Nevermind.

 

I had the same problem. The hissing led me to believe the diaphragm in my brake booster was bad. I changed the booster, and the problem was solved. Check to make sure your master cylinder isn't leaking. The leak can lead to premature failure of the booster. I had to run it for a few weeks without power brakes before I could afford the part. If you disconnect the vacuum line from the booster and plug it and the problem with the rough idle goes away, you know you have a leak in the booster as was my case.

 

Replacing the brake booster and master cylinder relieved the brake problems (mostly) - The idle is still intermittently rough... when doing so, brake pedal gets hard and oil pressure gauge and alt gauge start fluctuating. Still if I remove the vac line from the brake booster the idle is smooth which I'm guessing is just a side effect by adding more oxygen to a rich fuel mixture.