Here's my problem:
I have a '03 w211, E500, engine light came on and it was running rough.
I put gummout fuel injection cleaner in and eventually it ran smoother and eventually the light went out.
after the gummout/fuel was out and I refueled, it started running rough again and it started the same thing again-so I put gummout back in, and it eventually smoothed out.
When that was out of the tank, it started running rough again.
Am I missing something?