Here are Simons CIS primer causes for irregular idle during warmup in order (with my commentary)
Leaks in air intake system (false air) (Causes lean condition)
Auxiliary air valve does not open (Causes rich condition)
Cold start valve leaking (causes rich condition)
"Cold" control pressure outside tolerance (Could cause rich - depends on what side of the pressure range it is outside of)
Injector leaking, opening pressure too low (Causes rich condition)
Injected fuel quantities unequal (rich or lean but per cylinder - don't think this would cause surging)
Basic idle setting incorrect (rich or lean - assuming this means both air bypass screw and CO setting - with your symptoms we default to rich)
Lambda control system not functioning properly (Probably rich)
Here is calling911's post regarding CO setting w/o gauges. It is pretty cool. There is a link to Soukus' thread as well in this one.
http://forums.pelicanparts.com/porsche-911-technical-forum/387704-how-setup-cis-no-gauges.html
The CO adjustment port is to the right of the air sensor housing. Between the housing and the fuel distributor. If you get the allen wrench set - (Harbor Freight Tools (801) 426-9935 155 N State St, Orem, UT 84057) - read these posts first. Seems relatively simple but I have a later SC that allows me to cheat by reading the O2 sensor signals.
On sale, baby!
http://www.harborfreight.com/10-piece-t-handle-metric-hex-key-set-37862.html