I bought the kit from The Right Stuff Detailing. It's the same kit that several other companies sell. Picked it up at Carlisle in 2013.
Here is a link to the kit. https://www.getdiscbrakes.com/mdc62dc
When I bought it they said I didn't need to switch proportioning valves. After having brake issues I bought a proportioning valve from them. The one thing I thought was wierd was that the passages in the new valve were smaller than the ones in the existing. The new valve made no difference. I'm now wondering if they sold me the wrong one.
Another issue is the size of the booster. It takes up a lot of real estate under the hood making it almost impossible to change the spark plugs.
I am contemplating buying a Bendix set up from Dr. Diff. It would clean up the look under the hood and make the driver side of the engine much more accessible.
Feets- It's possible the sound could be coming from the bottom of the booster, and now that I'm thinking about it, after I changed proportioning valves I remember hearing that groan a couple of times, but much less noticable. It's hard to hear with the motor running. With the vacuum booster I just need to turn the key to on without starting the engine to have the vacuum pump kick on and give me vacuum at the booster.
I don't have a problem with a hard pedal or pedal fade.