First off, the #4 cylinder is the one furthest to the right, or closest to the coil pack. Is this the cylincer we're talking about.
Second, what was melted. The porcelain insulator and the electrode should never melt. Did you only pull that one plug, or did you pull all of them and that was the only one like that.
Thrid, try putting in another spark plug, or one of the old ones. Try that and see if it does it again.
Fourth, have you ever run fuel injector cleaner through your car.
Fifth, when was the last time you changed your fuel filter. It's too late now, but it could have let enough dirt through the filter to get in the fuel rail and partially block the injector causing it to run lean, and thus run extremely hot in that cylinder.
Sixth, does it run like crap all the time, or just at specific RPM.
By the sounds of it, you may either have a bad injector, or just dirty injectors. I would try taking them off and cleaning them. Might even be a good idea to take them into a shop that can do a bench test on the injectors for you, but I would just clean them first and install a new fuel filter. If you change one injector you should change all four, which is a bit pricey.
If you do decide after further inspection that you need to remove the injectors from the engine, don't follow the haynes manual. They do it the really friggin long way. Let my know and I'll tell you a shorter (1-1.5hr) way of doing it.
yes it is the plug all the way to the right and the entire tip was melted both times. I just changed that injector and I am about to go drive it around to see what happens. I also put some injector cleaner in my tank. I will tell you what happens later. Thanks for your help.