Ditto for my 722.6 - the erratic behavior was caused by a bad AMM (or MAF). And there was no CEL and no codes either. Whatever you do, DO NOT BUY THE EBAY ONE!!! I went through 3 of those within 3 months; fortunately the vendor was reasonable and replaced at no charge, but by the time I needed the 4th one I knew I would be pushing my chances with him. I got one from Phil - I think it was $200 or $250, but it has been a year and many thousands of miles and no problem. I now keep the 3 EBAY ones as spares in the trunk. They work OK, it's just that they have a "flat" spot in the power curve so acceleration isn't as smooth. But in the case of a total AMM failure, where the car won't run, these spares will be just fine.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280