C220 stumbling idle when starting

[tryfunke]

This 96 c220 with 95000 miles stumbles when starting. The idle moves quickly to 400 rpm I believe mostly when it is warm and the engine has been running. The car recently had a new mas air sensor I purphased form this part shop. That sensor has eliminated the engine lite and a rougher idleing problem with occasional stalling (low rpm when at idle) Spark plugs and the larger gas filter have been replaced. The car running great overall. It never stalls during operation. The only problem is the occasional stumbling with starting. If gas is applied, the stumble can be minimized. What do think could be behind this problem? Is there another gas filter to change by the throttle body? Thanks loads. tom