I have a 96 SL2 that until now has been running fine, but suddenly started running very rough (sputtering and extreme loss of power) when I started it up this morning. The check engine light also began flashing. I pulled the wires off of the plugs one at a time and notice there was no change when I checked one particular plug, while all the others caused the car to almost die. Plugs are fairly new. Any ideas??

Not much of a mechanic if you can't tell, but I can figure things out with a little guidance.

Get the SES Codes.

Replace your ECTS with a brass one from the dealer.

Clean the contacts of the coil towers getting rid of any corrosion.

its possible that fuel injector is clogged. If nothing helps, swap injectors with another and see if the miss moves.