Hi , my wife has a 2009 R56 "ac schnitzer " Cooper S , and yes our engine light is coming on about every 2 weeks , both 02 sensors have been replaced , when we connect our little diagnostic tool to the cars USB port , the sensors are working fine , it throws up the , yes you guessed it , 2188 code, running rich on bank one on idle or whatever , as i say sensors are fine , only thing it can be , unless someone on here knows better , is "super knock" and needing decoke of the inlet manifold with the bloody walnut shells , $ 720 Aussie dollars by our local BMW dealer is what it costs , havent done that yet , yes , service light comes on so factor that into the cost as well , thing is BMW say this is all it can be , problem is just supposing after work is done , the light comes on again , all we are doing and will ever be doing it seems is staring at this bloody engine light , at moment we are just cancelling light with the tool until we get car serviced , we have run decarbon cleaners through and through the turbo and fuel injectors and yes it is run on 98 octane fuel , can manifold be cleaned by us and with what easily , if we spend the money at BMW getting it decoked properly can we be confident that we wont have to keep looking at the light , car as done 100 , 000 klms , any ideas .