I replaced the fuel pump and filter on my 80 SC and it now "hunts" for rpm when started warm. The problem lasts for 30 seconds when started warm and does not exist on cold starts. I've seen similar problems noted here in the past and can't remember what the solution is.

Also on another note, I went to adjust my mixture and found that the mixture screw is stripped. Can these be easily replaced and what is the availability?

 

I am sure you can get the screw at Stoddards. I would try adjusting the mixture control unit a little bit at a time. I would say not to hard to change but I always say that so my opinion may be overly optimistic. I think you want to turn counter clockwise to lean. Just remember to count your turns so you can get back to where you started if neccessary. Also do not adjust with car running and turn only a tiny bit at a time, like a quarter turn. Did you try adjusting the warmup regulator. I believe the pin on the WUR would need to go up a bit to lean out. It sounds like your running too rich. The car when it is cold needs the extra fuel but when warmed up is getting more than it needs. I would start with the Mixture control unit. Having a shop measure the Co might be helpful too. Maybe somebody, will post the desired Co level. I Hope this helps.

 

On 80-83 911SC's with lambda sensors, you can also hook up a dwell or duty cycle meter to read what the injection system is doing. Monitoring through the duty cycle test connector, located on the left side of the engine compartment, around the base of the fuel filter with a rubber cap over the end, allows you to see what the frequency valve is doing to create rich / lean mixtures. Prior to that you needed the CO2 meter.