I got a 1998 cadillac deville and reading a p0308 Ive changed the plugs and wires checked the coils and the fuel system everythings to be in check this is as far as I can go DOES ANYBODY KNOW WHAT IT MIGHT BE????? THANKS mARK

 

Does it have an LS motor in it? Seriously, take it by your local Advance/Autozone/Pep-Boys/etc and have them tell you what the code is. Or, just Google it...

 

Im guessing you know po308 is a cylinder #8 miss, if you replaced plugs and wires after
the code, try moving the coil and injector from that cylinder to another cylinder and see
if the miss follows to the cylinder you swapped with. if it does, just move injector or coil
next time and see which one makes the difference. won't cost anything.