2003 Mercedes-Benz CLK-Class stumbles and dies after highway driving

Run the car down the interstate at 70- 80 MPH for 2 hours under the Florida sun. Get caught in stop and go traffic car stumbles and misfires and stops. After 10-15 sec can restart but will continue over and over doing the same thing replaced plugs, wires, power packs, fuel filter, crankshaft sensor,mas air sensor no help.Made a run from Largo to Daytona recently during the day something On the return trip at night kept it under 70 MPH for 3 hours no problem. Every time the light comes on it shows misfires cylinders 5 and 6 . Never doses it around town started doing it around 80k miles car has 100k on it now