I'd have no problem using the knock off plastics but be prepared to widen holes etc to get the plastic rivets to line up.

I'd maybe stick with OEM just for the seal that goes at the leading edge of the triangle parts that's a fairly complex design with several types of material where the knock off likely will take shortcuts that will greatly reduce the effectiveness of keeping engine smells outs of the cabin intake

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)