'03 Park Ave #4 Injector Not Firing

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A Customer brought in their Park Ave because their significant other severely screwed up the tune up after having a issue with frozen fuel lines. I recommended dry gas, they put it in then the plenum managed to literally explode after a bad backfire. (Before I was involved) The plenum was replaced as well as the intake gasket, then the #3 and #4 Injectors stopped firing. Apparently it turned into a hash match and 3 days later new front plugs, #3 Injector, Plenum, Gaskets, and Fuel pump were put in. They also managed to COMPELETELY screw up the plug wire firing order and after I fixed that it still runs rough. I put a noid tester on all the pigtails which they all passed, and even swapped out the one injector yet it still doesn't want to engage until the car's been redlined under load and THEN It'll fire until it's restarted. I haven't been able to do a impedance test since can't find the proper resistance anywhere to what the injector should be firing to.