its a 2000 flex fuel 3.0

Its not the actual injector. I think its wiring or computer.

no change in idle when I pull the injector plug. But I think I can feel the injector opening and closing.

compared to nearby injector diagnostic light flashes less brightly. but that's pretty hard to quantify

when I pull the plug on another injector it idles about the same but I can tell it surge up and down as I disconnect and reconnect it.

fuel injectors were backflushed and swapped same problem cylinder.

Where do I go from here just take apart the loom and look for abraded wires?

its the number one cylinder, passenger front.

 

Check for B+ at the injectors electrical connector at KOER. If ok, disconnect the firewall located computer electrical connector & perform a continuity check on the suspect injector return/ground wire. If continuity checks ok, suspect a computer ground switching driver/s are faulty. EDIT: If you come to suspect the computer injector ground switching driver, with your multimeter check the driver for lack of a pulsing ground continuity, when the engine is cranked. You can also check the ground switching by inserting a noid light in the circuit & watch for it blinking when the engine is cranked. Be sure to disable the fuel pump while test cranking the engine, so you aren't washing the cylinder walls down, loading up the oil, or pumping raw gas into the exhaust manifold to cause the cat converter to over heat on the next restart.
If you come to suspect the computer, if you can come by a like programmed computer from a like equipped engine, try swapping in the computer & see how it goes.
If you have, or can come by a scantool, have it perform a computer/controller trouble code scan to help focus your trouble shoot & post All trouble code clue Numbers.

 

Have you checked compression and spark? It definitely sounds like a solid misfire, but it also sounds like the injector circuit is probably OK if the noid lights up. If you have a stethoscope, listen to the injector while you disconnect and reconnect it. If it clicks, it's opening. A long 1/4" extension pressed against the ear works well, too.

If you have access to an oscilloscope, check the pulse waveform between this and a known good cylinder. If your hunch is correct, you should see significantly less voltage drop between the negative side of the injectors and ground on the injector that isn't firing when compared to the others. A high-quality DVOM with fast response and min/max peak monitoring may work well here, too, but a scope will show you what the voltage is actually doing in those few milliseconds when the injector is attempting to fire.