Why won't my Ford Expedition go over 20 mph and runs really rough

You “and your buddy” have placed the plug wires in the wrong firing order position. Google will have helpful pictures of firing order.

Hello, naturally if you have a 5.4L engine, your coil boots are probably not capable of insulating the spark any longer having taken them out and reinstalled them. If this is a coil on plug 5.4L V8 application, you simply must replace coil boots at the time of spark plug replacement or you will risk major misfire under load after reinstallation. If it is a 4.6L, yes, as pushrod said -- wires are likely misrouted. And in either case, there's a slight chance of exhaust restriction causing no performance too -- but that's a 5% chance compared to the other factors.