Just a little info to pass on. My 98 ML320 had a rough idle problem (especially in drive sitting still) and would shut off at a red light or stop sign on occasions. Replaced the MAF, plugs and wires, fuel pump and filter, air filter and cleaned the EGR tube to no avail. My local mechanic told me to check and clean the butterfly valve on the intake. I took the intake tube off and checked it out and sure enough, it had a ring of what looked like hard carbon build-up around it keeping the valve from functioning properly. Needless to say I cleaned it off using MAF cleaner and it runs like a champ! No hesitation, sputtering or rough idle anymore. Hope this helps anyone having the same problems!