Mine doesn't have a spacer on it either on any of my cars. This idler gear is used on SLS suspension, but it doesn't have to be an "S" Class. Both of my 300 TDT's have the SLS pump on the front of the ehad to keep the rear shocks inflated when loading up the wagon. I don't think this is a big problem, but how loose is your chain? Is it under proper tension?

Having worn out guide rails and stretched out timing chains are going to be a bigger problem than a little play in the idler gear!