If you can't get techron, just get a nice high grade fuel injection cleaner from the auto parts store. Look for one that promises to clean both the fuel system and the intake valves. I've just noticed that others don't seem to keep the car as smooth when in the tank-- techron in the tank actually improves the driving, some of the others will be a little rough until they are run through the car (just a subjective unscientific observation.) It tried the MB luby stuff (it's in europe) and didn't like it-- get one from a high end supplier and pay them the extra 5 bucks/2 pounds/etc

Next, I never did check to see if your car had an idle control valve. Yes these are known to cause idle problems. I also recommend checking them for SL owners like myself and on those cars they can be cleaned. MB charges and arm-and-a-leg for the same idle control valve you can buy online for 1/4th the cost (the SL is made by VDO). Anyway, you should check the idle control valve and the vacuum connections to it. Try cleaning it.