CLS500 4.7TT 2012,, SL350 09, 996 cab, all current. Gone :CLS 55 E500 W211, 2x M5s and too many 911s
Rocker covers often leak , as do the breathers. Engine mounts are food and drink to these engines and make a huge difference when changed if they have significant wear/drop. The other thing that gave me a very poor idle was a disconnected vacuum pipe. Your intake pipe may also have the same effect. Mine was eneven enough to cause the EML to come on.