From the description of your symptoms, it sounds as though it may be fuel related. Start simple and replace your fuel filters. How many miles are on the car? Has the timing chain and associated elements been replaced on schedule?

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold