surging 2000-3000 rpm

[Oldporsche]

I test drove an '80SC with 75K miles. The car was in very nice shape. It recently had a tune up on it.

The owner brought it to me complining about the idle speed and the fact that it would search for idle. I first checked the car for vacuum leaks. I found a hose on the passenger side of the motor that seemed to belong on one of the diaphrams found on the right side. I tried it on one and the idle went way up. I tried it on the other and the idle seemed to smooth out a little. I had recieved help from John Walker on the idle setting. I found that the motor didn't seem to react immediately to the setting of the idle screw. I have several questions about these events.

Car: 80 SC
1. This car has a light surging at partial throttle between 2K and 3K when driving down the street. Any ideas?

2. What are the two diaphrams on the right side of the motor for? Where do the operational hoses go to for both of them?

3. I was looking at the mixture adjusting plug on the fuel distributor. I found that the end of it was missing and the plug was just sitting in the fuel distributor housing. I couldn't tell if there was vacuum there. Will it leak vacuum there?

Thanks a lot.

David Duffield