Update - Returned suspect MAF sensor and got another one. Installed and the car runs GREAT.... it can breath again !.... stumble and hesitation gone. response much improved. Now that I compare this MAF sensor to the first one I picked up, it looks like the first one was either a returned core or a bad part restocked. The working sensor was in a sealed box and the wax paper wrap around the part was fresh and unwrinkled. The former part's box and wrapper was not so new looking.

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Jeff
'87 300E
'92 400E
'06 ML350