I won the lemon law and DC replaced the car with a new XFire.

The ticking sound should not be confused with that of the normal tappet sound driving at around 2,500 rpm's in a low gear. My ticking sound was present at idle and at a high gear (6th) while on the freeway at 65-75 mph. When you're driving on the highway at 65 mph and you hear the valve train like if the engine was inside the car with you going tick-tick-tick really fast like mine did, then you have the same problem I had - and that's not normal in any car. The ticking sound just got progressively worse and louder and more apparent to the point where people were asking me why my car sounded like it had an exhaust leak-when it didn't. It was finally diagnosed by the service manager when i asked him to park the car isolated away from the service bay ambient noise. I asked him to park the car between two parked cars in the lot away from noise and just let the car idle and he heard it loud and clear. Mind you this was after the 4th attempt at getting them to hear the noise. Also when at a fast food drive thru when you're about to pay at the window you could hear the sound bouncing off the wall.

These engines by nature sounds very diesel like and are very thin walled alloy enabling you to hear a bit of tappet sounds but once the car is underway the tappet/lifter sound should fade not be louder and louder as the cars speed increases. The ticking (lifter sound) i'm referring is identical to that of a faint exhaust manifold leak.

I'll try and come up with the TSB from Mercedes and post it up for you guys. I know someone else on the forum, can't remember who, had the same problem where he got the cams, valves, lifters, etc replaced for the exact same noise.

Plus, the dealers had all kinds of answers and excuses for me like using the wrong fuel, or the engine is supposed to sound that way (WHAT THE HECK THEY KNOW THEY NEVER HAD THIS ENGINE IN THE PAST ON ANY CAR ITS A MB ENGINE), etc...