I went for the OEM look carbon fiber diffuser from
Mars Performance (Australia). Love the wet look. Good weave and good fit. You do, however, have to let them settle in, and maybe even make a later fit adjustment to get it exactly right.
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Current: Alpine White M140i F20 LCI-2, 250kW/335hp, 2018.
Sold: Melbourne Red 340i F30 LCI Luxury Line MMPK - 265kW/355hp, 2016.
Sold: Alpine White 123d e82, 2010, 150kW/204hp.