My 260E is pumping out black smoke. I've had it to a Mercedes dealer with no luck and talked to another Mercedes mechanic who is stumped. The cat gets hot but not red. When I first start it up, black soot comes out of the tail pipe. I have replaced the O2 sensor, the temperature sensor, the overvoltage relay, and am thinking about replacing the electrohydraulic actuator.

Also the car runs ok when it's cold but as it warms up, the economy needle drops and smoke starts coming out the exhaust.

Any help will be appreciated.