What are the symptoms of a failed warm-up regulator?

I've been throwing parts at my 450Sl for two months now and still can't drive it. It has been getting harder to start. Idling rough in D ok but not perfect in P. So far work I've done: Distr. cap & rotor, set timing to TDC, new addtl. air valve, cold start valve, thermo-vacuum valve, plugs and wires, coil, checked all vacuum hose against the diagram and all are in the correct spot and in good shape. I tried to set the CO/idle using my father-in-laws gas analyzer and can't get it below 6% CO no matter how lean I adjust it. Could my warm-up governor have failed. The car ran much better earlier in the year when it wasn't so hot outside. I would like to drive this car this summer but I cant get the thing to idle decently enough to sit at a stoplight without the fear of it stalling. I need help please.