With my SL 600 some time ago the problem arose that the right cylinder bench did not go along with the cold start. Run after a few minutes and a subsequent at least about 20 minutes break the problem had disappeared and the engine ran round the whole rest of the day. In the last weeks the problem got worse and the engine ran round again and again. After it had just gone out twice at the traffic light the workshop advised me to change the right ignition coil. A lso I bought a new original ignition coil from Mercedes and had it installed including new spark plugs. The engine ran exactly 2 days great. After that the problem occurred again however this time at the left cylinder bench. Once again visit in the workshop, led to a new engine control unit being installed. Now the car runs well in cold condition, but as soon as the engine is a little warm it starts to run round, the vibrations go into the steering wheel and it still has I’d like to buy an OBD device for myself. Which is the best one for the SL 600?