Mine is a diy special , but was fitted in acordance with the LPGA guide lines and is fully certified. That is the secret, the certificate, make sure you get one. It made no difference to the insurance. You don't have to do anything to change over, just drive, it changes over itself at 1300 rpm if the water is above 30 deg from cold start and you won't even notice (except the light will change on the gauge) I won't ever go back to diesel.