The wheels and black headliner are the real indicators. All 135i have the same front and rear bumpers so that tells you nothing. All that M sport gets you is the wheels, black headliner, and M door sills. That's it. I have never seen an M sport car without the M sport wheels (from the factory) so that source is incorrect.
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2014 CC R-Line DSG | 2010 S4 Sold | 2010 BMW 135i Retired | 2006 Lotus Exige Sold