It is my understanding that the efi on the 300 is basically unprogramable, as far as understanding modifications (such as injectors, cam, boost, etc). Why is this? Is it impossible to program a chip for serious mods? Or is it the initial expense of programing a chip (or getting someone to do it correctly) that is ridiculous? If you have to get technical in answering this go for it, I would really like to better understand what I am dealing with. I have searched archives etc. and only came up with discussions who has obd1 or obd2 which were not definitive. But mine is obd1 I am sure because it is in a 95 1/2 ton truck. Again I would really like a good explanation on why this computer is not programable or difficult too. So all you techs please feel free to jump in. Any and all help and info greatly appreciated. Thank you for your time.