My MB Dealer performed routine B service recently. They also replaced two engine and one transmission rubber mounts that were deteriorated (119,500 miles) and the right side valve cover gasket. After I picked up the car, I noticed a slight engine noise while driving that was not present before the service. It's not present while the engine is idling, or reeved up, only when you give it gas/accelerate. My guess is that the mechanic may have dislodged or broken a manifold gasket when replacing the engine and transmission mounts which is causing an small exhaust leak someplace. After driving my vehicle for almost eight years, I'm pretty knowledgeable about the sounds my vehicle makes, so I know that I'm not imagining this noise I'm hearing......even though the car is operating well, the noise is bugging me. My question: Is my guess that the noise is an exhaust leak, can my MB Dealer diagnose this issue with their test equipment and/or will the vehicle's internal diagnostics identify the issue? Or should I just let it go and have my MB Dealer check it out during my next service there? Don't know if there could be some damage to the engine if I just ignore it?

Okay......I just returned from my MB Dealer and had their shop foreman ride with me to hear the noise. He diagnosed it immediately. During the service visit, the mechanic had added a fuel treatment which dislodged some of the carbon build up in the engine, and that carbon is igniting earlier than the fuel combustion and causing the "ticking" noise. The foreman said his car did the same thing and after a couple months, if it hasn't cleared up, add the Chevron Tectron fuel additive to help clear it up. Glad to know that I wasn't "hearing bogus noises" that weren't there before I took the vehicle in for service. He also said the Sunoco 91 octane fuel is fine for the vehicle, that's not the cause. If anyone has any other suggestions on how to clear out the carbon, please post it.