how much is the 335i cap?
German Auto Solutions sells a 1.2 bar cap in anodized black and red, as apparently they think the system pressure is too high as well. Its 35 bucks, but I'm definitely going to put a lower pressure cap on my X.
If the 335i cap is cheaper, and fits our expansion tanks, let me know and I'll get one of those man!
EDIT: I don't think the 335i cap fits the M54, but it might cross reference on the 8 cylinder expansion tanks!
Here is the link for the GAS cap:
Buy G.A.S. BMW 1.2 Bar Coolant Cap