Hopefully I did. I didn’t find anything on our site about the head passages blocked with carbon? But found lots on Mercades searching. Maybe I should include that information in this post. Look for The large hose that goes from the air pump to the left & right head actuators. Remove the hose from each head actuator & start the car when it is cold. For 90 seconds you will hear & smell exhaust from the open actuators. If you don’t remove the actuator & retry when the car is cold again.
if you now hear exhaust then there is something wrong with the actuator function. If you still do not hear exhaust then the head is plugged with carbon. If the head port is plugged do a search on 2004 slk 320 sites & you will find methods to clear them & a more in-depth description.