I've just had my C270cdi tuned through OBD tuning to increase bhp and torque. I took delivery of the car on 1 March 2004, although the car was quick in standard mode, this has mede a real difference especially mid-range. However, I noticed yesterday that the Engine diagnostic warning lamp has come on. Does anyone know why this is? Could the OBD tuning have caused this? Any comments would be welcome.