Only a select few know how to tune the S54 ECU (Conforti, Nick G, Shadowman etc.) Those guys have developed a software SharkEdit to allow you to due a self tune or run maps that they provide. It was due to be released last year but Conforti heard that a group wanted to hack his work. From what I understand, Conforti is busy doing some encryption and has not set a date to release the Shark Edit.
Good luck with your quest.