1. CLK 320 A couple of days after a service the engine response was jerky and sometimes there was no response when you accelerated , especially after Engine breaking. Checking a few posts it pointed to the MAF. Checking I found that the air cleaner assy was not sitting snuggly on the MAF housing it is a very neat fit so after seating properly it has been OK. 2, ML 270 cdi Over a period of time I noticed a lot of black smoke when accelerating, this however disappeared but revs limited to 3000 and no kickdown but no warning light . This 3000 rpm limit was coupled with a less than smooth engine. It was intermittent and would disappear for days. Eventually it came back and was there most days. Again a search on here pointed to the MAF and of course to get the codes read. I disconnected the MAF and found that it made no difference - same 3000 limit and no kickdown. In a period where the engine was OK I disconnected the MAF and got the fault back. A quick inspection showed the MAF to be clean. However a clean with electrical cleaner to make sure and on the next drive everything was OK. Next day the fault came back. Getting the codes read was £80+ Vat so.... Off to the dealer for anew MAF £49 +vat and after fitting the engine is smooth Revs to the limt, kicks down and seems a lot quicker than I remember Thanks again to all posters.