The YouTube video in JPNinPA ,s post is an excellent one as scanner danner is my mentor . You probably don't own an occiloscope so you won't be able to perform the test as per the video but you get the idea of what to look for in terms of a fault. Diagnostically , the video mentions what is a valid test and what isn't but at least a continuity test can be performed to verify if a short exists . You must unload the power circuit BEFORE you attempt a continuity check. You will have to remove the power from the circuit by removing the fuse that powers the injector circuit . When there is no power in the injector harness , the circuit can be safely checked . Be sure your checking the power side and NOT the ground side . The ground side is controlled by the PCM . Don't want to mess with that for this test. You should have a wiring diagram to better understand this circuit to know that you've removed all power from the circuit to be safe . If you have a computer safe test light , you'll know for sure your checking the right side. Usually the ground side will have a tracer ( stripe ) on the color code on the insulation of the harness plug wiring but consult the wiring diagram to be certain . If touching ground with the continuity tester and the injector plug power wire of the injector in question causes the continuity tester to light , there is a short . It's not a difficult test but please understand the fundamentals of the circuit first before attempting this test . You don't want to introduce voltage , even penlight voltage , into a live circuit . That is a no no . Always test the circuit for voltage first before doing a continuity check. Before performing this test , you really should inspect the harness to,verify visually if any damage to the harness exists. I don't know what testing was performed prior that you've mentioned and was said that the wiring is alright but keep in mind that the troubles codes still exist and are referenced to high voltage in the circuit which indicates constant voltage present due to a draw that is caused by a short. The power side of the circuit is always live when the ignition is on and the injector only fires when the PCM grounds the injector when needed but the code is set when too much voltage is found by the PCM upon grounding the injector and excess voltage feeds back to PCM. That is why a short must be looked for as that is the most likely cause of your drivability problem. You posted that it is stronger in reverse . Keep in mind that the transmission has more power in reverse than first in any transmission so,the engine is under more load and the problem will be felt more in reverse than in drive. That is somewhat irrelevant since the problem exists regardless. Bottom line is that the injector for each cylinder that the DTC fault was found on is over active . The duty cycle of the said injectors for the said cylinders is higher than the rest of the cylinders on the engine . A good multimeter with duty cycle in percent scale can find this easily. The two cylinders will have higher duty cycle that the rest . But the main test is the test for short circuit. If your hesitant to proceed citing possible error procedure wise , please let someone who knows these test procedures well to do the testing . Will respect the decision not to cause further damage. But the testing for a short needs to be performed.
