P0300 2005 LQ4

[Stepside_fever95]

I have a 1999 K1500 Suburban that I swapped a 2005 LQ4 6.0 in. The engine has new acdelco 41-110 spark plugs, MSD Superconductor wires, green intake manifold gaskets, and stock coils and injectors.
Last night coming home in heavy rain it started to misfire really bad and the CEL was flashing constantly. The vehicle was shifting oddly as well probably because of the misfiring. I manually shifted down to 1st and gave it full throttle and it did fine until I let out and put it back in overdrive.
When I got home I looked on my scan tool and it was shaking cylinder 2, 4, 6, and 8 misfing with cylinder 6 misfiring the most. Today I have checked the injector pulse and swapped coils around and found nothing. My fuel pressure at idle was 52psi and 55 with the key on and engine off and held pressure. After looking at things I hooked up my scan tool and now im getting a few misfires on bank 1 as well.
Does anyone have any ideas as to what it may be?

The screenshot is from last night showing the instantaneous misfire count.

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[skylark]

Check the connections at the coil harness. I've found loose pins and corrosion there before.

 

[Stepside_fever95]

Check the connections at the coil harness. I've found loose pins and corrosion there before.

The connectors looked good, I keep dielectric grease on them too. I'm still kinda stumped as to what it is. I played with it more yesterday evening and now it's only cylinder 6 and cylinder 1. I think I'm going to pull the injectors and clean them good and see what that does.

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[brianmcb]

Id be looking at your o2 sensors. Pull up the data for b1s1 and b1s2 sensors.

95 rcsb, L33 5.3, hot cam, hp tuners, 4/6 drop

 

[Stepside_fever95]

Id be looking at your o2 sensors. Pull up the data for b1s1 and b1s2 sensors.

95 rcsb, L33 5.3, hot cam, hp tuners, 4/6 drop

Bank 1 sensor 1 and bank 2 sensor 1 are both reading around the same voltage. I deleted my b1s2 and b2s2 o2s.

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[Stepside_fever95]

I decided to pull the fuel rails off to clean out the injectors since I had been planning to do that anyways. I also decided to replace the fuel filter as well (only 15 bucks so why not? It's been several years).
While I was putting everything back together, I noticed a wire had come undone from the plug going to the knock sensors. I rewired that and now it runs fine.
I still have a misfire only on cylinders 1 and 6 at around 2000-2500 rpms. I'm still confused as to what is causing this, but it's not severe and runs well otherwise.

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