Can someone explain how the computer on my '96 controls the timing? If the base timing is 4 deg and the full timing is 24 deg does the computer just advance the timing by 20 deg assuming that the base timing is set correctly? Or does the computer know what the actual timing is at all times and adjusts accordingly no matter what the base timing is set at?

 

The computer advances the timing based on RPM's. At idle the computer advances the timing very little if at all. The timing advance increases as the RPMs increase. The computer only knows where the base timing is set at. If the base timing changes the computer won't know it has changed.

 

I'm concerned my truck won't run as good once I retard the timing. Right now when hot it will barely crank.

 

It's not. On every Ford EFI I've ever seen, it's 10°. That's probably the whole problem. Follow the tune-up procedure on the emissions sticker (with the vacuum map) and use the base timing indicated on the white sticker, probably on the front of the valve cover.