I read your thread and have a thought as to a possible problem that might cause your symptoms. This idea actually applies to all makes of fuel injected cars. My sister has been having trouble with her Mercury where on cold days the car will not run properly. It will start, sometimes run fine, other times will stumble and die, and other times revs up then dies. It will not idle good till it warms up. Sometimes it will even stumble and die when stopping at a stop light. On nice warm days and in the summer it runs great.

After doing web research, I discovered this can be a common problem with fuel injected cars. What happens is air will get sucked in after the intake inlet (after the mass air flow sensors, or in this case the flap on the fuel distributor) and mess of the fuel/air mixture. This will cause the engine to run lean. The problem becomes a lot worse when the weather turns cold, and may go away when the engine warms up. Common failures are cracked intake gaskets and injector seals. In the case of the SL, it has a lot of places air could get in with all the vacuum lines and such. The SL even has air injection lines that go to the injectors that could be leaking or cracked. I know first hand that cracked and leaking vacuum lines can create a rough idle.

So maybe it is not a lack of fuel creating the hard starting, but too much air. The oxygen sensor would sense a lean mixture and turn the light on.