If I was a betting man I would say it is your OVP.....are the symptoms as follows;

Stalls out of the blue...won't restart straight away...leave it for 5-10 minutes and will restart and all will be fine etc etc. May also have a stumbling idle

If it is, its your OVP....the original relays had a design fault in them which results in the internal soldering breaking down and causing intermitent stalls....this will get gradually worse.

Sad to say that the expensive MAF replacement may not have been required....OVP relay will cost you about $60 and on my Right Hand Drive C280 its up by the ECU's on the right hand side of the engine bay. Silver relay about 3" high with a fuse on the top. Takes 5 minutes to replace.

Good luck

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Current Mercs
R129 1994 300-24SL
W124 320E Turbo Technics Twin Turbo 350bhp

Previous Mercs
W124 1986 Quad Cam AMG Hammer, 45,000 miles
W124 300E Turbo Technics Twin Turbo 320bhp
W124 E500