Based on this info I'd rather pay the extra $$$ and get the ///M stamped parts. They could well be the same but I'm prepared to pay the difference to ensure they are full M spec.
BMW 135i N54 TWIN TURBO
Quarter Mile firstname.lastname@example.org - Street Tyres
Queensland Raceway Sprint 1:01:22 - Street Tyres
Queensland Raceway Clubman 1:04:74 - Street Tyres
Lakeside Raceway 1:03:97 - Street Tyres