I have a 1990 ford f-250 5.8L and it won't idle or run rite I have to hold it full throttle down the road or it will not run rite

Well, I have two 5.8L Fords and this sounds kind of tricky for sure. I've had my 1990 5.8L idle up and down with lots of variation. Sometimes it would jump to 1200 RPM and then fall to 400 and then back to 1200. Really irritating. If you look on the very top of your engine, there should be a round shaped black plastic cover piece covering the top of your throttle body. Your throttle cable travels up to this area and if it has fallen out of the U-shaped retaining groove and is just flopping around this might explain why you can't keep it going unless you push the throttle pedal all the way to the floor. You should be able to just push up under the lower edge of this black plastic top (flexible) and see if the throttle cable is not properly set into it's retaining groove location. Also if that plastic piece gets broken it will just flip flop all over the place. You can also loosen the bolts to the cover and just take it off to get a better view. It might be more complicated than this but that's a start I hope. I've bumped mine while doing maintenance before and had a similar experience. Good luck!