My 2015 RC350 F Sport (27K miles) sounds like it is a loud diesel engine at idle speeds. Have had the Lexus field service guy listen to it and he says its the fuel pump and this this is normal, so they won't do anything about it. It never used to make this dreadful noise. I have complained to Lexus customer care and they say if the rep says its ok nothing more can be done. Any suggestions???