"Solving Bosch Continuous Injection System (CIS) Problems" by James Weber is a good start.
Also go to Rennlist and find Jim Williams tech articles on the subject.
Pelican has good info in their tech section as well.
The idle does not normally fluctuate due to WUR issues. Many things (unfortunately) contribute to idle quality. There are various thermal and time switches and valves that regulate idle during the warm up cycle. What you are describing sounds like the initial cold start idle is set too high and then comes down too low when warm. Is that right? Have you bench tested your AAR? Vacuum leaks on the hoses connecting the cold activated CIS components?
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8