Well, you are going to have to do some testing. All the injectors should have 12 volts to one side all the time (same color wire). The ECU applies a ground to open the injector for a certain amount of time. Since it is 2.9 it is batch fired, meaning you should have three injectors firing at the same time (so you will have two different colored wires going to the six injectors). It isn't like true fuel injection where fuel is injected into each cylinder. The injectors just push fuel into the manifold and each cylinder just sucks it into the individual cylinders. So I don't think injectors would cause a steady miss on any one cylinder. You can google how to test the circuits.
Fuel pressure would not cause a steady miss on any one cylinder.
Since you said you have a steady miss, I think it is much more likely that you have a spark problem.
Most of that is right, but some of it is very wrong.
First, all the info about wiring is correct, you effectively have 3 wires run for all 6 of your injectors, 1 to power all of them, one to fire left and one to fire right. The 2.9 does however use "true fuel injection". The system it uses is know as a batch-fire ported injection, meaning all the injectors on one side fire together, and they are pointed right at the intake valve. The system that enjr44 referenced as his example of "true fuel injection" is called direct injection, and has only become even somewhat common place on gas engines in the last 5 years, but has always been used on diesels.
Anyway, since the 2.9 fuel rail is made of regular steel it is not unheard of for the rail to corrode inside, and then when the engine doesn't get run for a while that crap can get into the injectors. Since 1 and 4 are at the front of the engine they get fuel last, and will be less prone to plugging up.
Make sure you are getting power and pulse to all injectors (I'm a little unclear how you determined which cylinder were and were not working). A 194 bulb in a socket with the wires stripped back and pushed into the pins of the injector plug will glow dimly at idle and get brighter as the engine is revved. This is a quick and dirty test for injector wiring. It's not precise, but it is accurate.
Should that check out, I would pull the rail out, remove the injectors and inspect the inlets. If you find crap in there I would try cleaning the inside of the rail with muriatic acid and then flush well with mineral spirits, and replace the injectors.
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