I am reletivly new to the forum after many years of Golf ownership (Seen the light at last). Anyway just bought an A4 Avant quattro 110 tdi which was a bit sluggish and I diagnosed a MAF problem, Nothing unusual there then!!! I found out from another web site that a Mercedes part would fit so thought I would give them a call. Anyway the mercedes part is made by pierburg and looks far more robust thn the bosch original. I have had no problems with extra smoke etc and the car is still returning 50 mpg on a run. The best part is that the Merc MAF is only £41 + VAT not £120 or more. The part is a direct replacement, even the plug fits but you have to cut off a couple of locking lugs on the new part. Hope this is of use.
The part number is:-A 611 094 00 48