2006 GMC four-wheel drive 5.3

Had a interesting day today hooked up my scanner to this truck had multiple misfire code po300 and a lean fuel trim code bank 2 don’t remember the PO for that so I pull up the fuel Trims on both Banks short-term long-term and sure enough bank 2 was running in the high 20% range bank one was running normal so the man that owned the truck told me it probably just need it plugs and wires I said well let’s find out if it needs plugs and wires did not really believe so seeing as how it was only really misfiring on bank 2 but we have to prove all things so the first thing I did was made sure that I had Spark on the coils then I decided to take a couple of wires off and do a resistance test from bank 2 seeing’s how I did not know the correct specifications for the resistance on the wires I did know that bank one was not misfiring so I pulled a wire off of Bank One did a resistance test on that wire came up with the same resistance so that ruled out bad resistance in the wires the wires was good so then I decided Well I would pull a spark plug and see how it looked very black not with oIL more of a exhaust black almost like it wasn’t getting enough fuel to it so I decided I would check the fuel injectors so I back probe the fuel injectors and was getting power to the one side with the test light and getting the pulse on the other side so I knew my injectors was at least getting power so I decided to go one step further and unplug the injectors one at a time and listen for a change in the engine yes there was a change before all of this was done I also checked for vacuum leaks on and around the intake that was the first thing I checked for was vacuum leaks all of this being done I am trying to rule out what would cause this problem to affect just the one side so when I had pulled up my O2 sensors and short-term long-term fuel trims I had noticed that my bank 2 sensor 1 did not seem to be acting right so I decided I would get under the truck and look for exhaust leaks thinking that it could affect my O2 sensor what I found was that someone had cut off the Cadillac converters and replace those with straight pipes but left the O2 sensors and I found no exhaust leaks so I start thinking that well maybe there is a problem with this bank 2 sensor 1 O2 sensor and I decided I would pull the two front O2 sensors Bank 1 and 2 and swap them a round if the problem swap sides then I would know I found my problem so I pulled them out and I had found when they cut the exhaust they had actually cut into the O2 sensor so I went ahead and swap them over anyways and sure enough the problem swap sides went and got a new O2 sensor problem fixed just would like to say thanks to Matt I was able to understand all of this with the fuel trims and O2 sensors and make a correct diagnosis and not go off half-cocked throwing parts at everything that look like needed it all and all was a very fun day