I have asked several GM service managers and can't get the same answer. (some say its a reprogram of the computer - gas cap and decal, others say its a replacement of the fuel rails - fuel pump - and reprogram - and still others advise that it can't be done). I have spent several hours on the phone with GM tech and can't get an answer / they just refer you back to the dealer’s service manager. So, my question, I am in the process of purchasing a new 2008 GM with a 5.3L motor. What is involved in having the GM dealer convert the 5.3L motor to a 5.3L – Flex Fuel E85 ??