MFI is not EFI and has it's own unique quirks. Befroe you go messing with it, be sure you know exactly what you are doing and why. There are literally hudreds of posts on here, Pelican Parts BBS (
http://forums.pelicanparts.com), and the Early 911 S Registry BBS (
http://www.early911sregistry.org/forum/index.php) on the topic.
Most of the ones that actually help you will tell to to obtain, read and follow "Check, Measure, and Adjust" (
http://www.pelicanparts.com/techarti...ure_adjust.zip) to get your MFI top notch.