I really don't see any reason why stainless steel brake lines would cause your brakes to make noise. One of the easiest solutions is to use anti squeal pastes. Available from Autozone. I believe that BMW is also supposed to use it when replacing brake pads. Part number 81 22 9 407 103.
E92 M3 DCT - AiM EVO4 Data Logger / AiM SmartyCam HD / KW Competition 2-Way / OMP ARS Racing Seats / Brembo GT 365 / Pagid Yellow RS-29 / Rear Seats Delete