The ONLY aluminum valve cover I would use is the Genuine M56 valve cover, which includes a better CCV design...

I have seen a few complaints about fitment of the asian-made aluminum M54 valve covers. Though I have heard about cracks and warpage on plastic valve covers, I have never had a problem with any of the plastic valve covers on my BMW's - more than 6 vehicles...and I have several spare valve covers from previous engine rebuilds on the shelf...

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'99 E39 528i 5-speed 130k
'06 325Cic auto 115k
'05 X5 3.0 auto 173k-SOLD
'03 530i - manual swapped - 430k miles-SOLD