A week ago today I filled my SL on the way home from work. All seemed normal. About two hours later I went to leave and the engine was running rough. Not quite as though and entire cylinder was missing, but there is a loss. My guess was that I got a tank of bad fuel. I have been able to continue to drive the car. It has never stalled and above 2,800 RPM's the issue SEEMS to go away. I just refueled the car and have drove enough that the new gas should be well in the fuel system. I am puzzled as to what this could be. I would think that if it were a fouled plug or leaking injector I would get a Check Engine Light, but it has never been triggered.
Any thoughts?
Thank you in advance.

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Current:
1985 300D aka Miss Margaret
1991 300SE aka Alarice
1995 SL320 aka Samantha
1997 K1500 Silverado
Past:
1999 E300 ex-wife got it and let her son ruin it
1984 190 2.3 ex-wife got it and let her son destroy a great car
1985 300D (CA version) aka Maybelline lost to deer at high speed.
1981 300D aka Madeline (went to salvage at near 400k) rusty, yet best car I ever drove
Wishlist:
McFarlan TV6 (only a few privately owned)
ReVere with Rochester engine
1917 Premier (only one left)