Idle bounce or hunting

[Jamie911]

I have a 77 911 SC that has a 83 or 84 3.2L engine that has a newer non CIS fuel injection system. I guess that's the Jetronic system? I'm not really sure. Most of the time the engine runs great except when it is first started. It starts fine but I get a lot of idle bounce or hunting. Aside from the posibilities of vaccumme leaks I was told by a mechanic to lower the idle as my idle is set too high and that could cause the problem. It is currently at around 1200 RPM and should be around 850 RPM. The problem is I'm not sure how to adjust it. I was told it is done by using the hex head screw front and center on the throttle body but first you have to jump out a couple of pins on the diag port. Does anyone know what pins I need to put the jumper on. I tried a few combinations and found a couple the brought the idel up but the rest did nothing. Also when I did jump out the pins and turned the hex head idel screw it did nothing. Is that the actual adjusting screw or is it just a cap and the screw is under it. Any help would be greatly appreciated. If someone has a pin out diagram for the diagnostic port that would be great. Also if you know of a good book on this injection system that would be good also. Thanks.