Well, I fnally did a Engine running test with the OBD1 code reader. Other than a few miscellaneous codes that should have nothing to do with the issue at hand, it showed a problem with Cylinder #1. Indicating an imbalance. Book states cause could be plugs/wires(those are new, so shouldn't be an issue), rings/valves, and fuel injector.
Since injectors have been discused before, it looks like that is what is going to get fixed next. Just to make sure I don't make the problem worse, should I replace all of them? Or can I get away with justdoing the one?

 

if you can target out the faulty injector sure id say change the bad one only, especially at probably near 40 to 45 bucks per injector for your explorer. The only thing i would suggest though if doing just the one is get new seals for them all. them seals could be about gone anyhow and when you go to pull the fuel rail/plenium up to get the one injector replaced it could cause further problems with them old seals if they arent replaced.

 

take a look at your crank positioning sensor and the cam sensor, my buddy had a problem with his ford explorer and it took us a long time to figure it out, make sure the connections are right and whatnot, and make sure the sensor itself doesn't have any deeper grooves than what is already in it

 

You can rule out the ring and valves just by doing a simple compression test on the engine Id do each cylinder if they are all within range and there is no huge differences between each cylinder you should be fine on leaks there. If there is a bad piston ring orbadvalve or valve seat it would show in a compression test.