I have an SE engine, but I have been told that the SE was pretty much a direct replacement for the SL. I ordered my wires and plugs off this site (fastlane). They are Bosch W7DC plugs.
Fastlane shows these to be the right plugs for the SL and SE (I went ahead and ordered the ones on the SE page).
The car has been in the family for a number of years, and my father told me there used to be some kind of booster on the coil. He doesn't remember what it was exactly, but he said that the thing burned up and the car was never been the same since.
Maybe the previous owners knew it was running really rich and had the booster added on. I guess that would make sense. What exactly does a booster do? Up the voltage and make a bigger spark?
How do I go about evening out the mixture?