I don't believe it's emissions, but rather noise restriction. There are a few threads covering this and how there are two exhaust systems on the 1m, Chinese market and non-Chinese. Very unfortunate, but not irreversible.
1989 E30 M3/Zinnoberrot
2011 1 Series M Coupe/VO/Fully Loaded/Bloated/Stoptech ST-40 Trophy Street