E420 Ehaust leak

[knarf]

Good Evening Forum Members,

I just purchased a E420 with 118K from a dealer, 09/07 production.
I did a short test drive, carfax and VIN check.
The car started up and drove fine until left to idle after the drive.
While idling the car began to misfire and stumble, no dash fault lights, i.e check engine came on. The low fuel indicator light was on so the dealer drove the car away to add premium gas. When he came back from the gas station the car was idling properly. He suggested that that was the problem.
I picked the car up today and while driving home, less than a mile from the dealership, I pulled over to let my son drive the rest of the way home. Again while idling the car began to missfire and shake. I detected an exhaust leak in the area of a exhaust pipe connection just after the cat. The words ELECTRICAL and CHECK ENGINE light came on and a strong rotten egg smell was apparent. I drove the car back to the dealer and left it for him to diagnose and repair.
Has anyone had a similar experience and fix or might know what the problem could be?
Can an exhaust leak cause these symptons and warning lights?
I'm nervous.

Thanks,

Knarf