Need help with weird misfire
 

So I drove through a puddle of water a couple nights ago that was much deeper than I thought it would be. After that it developed a misfire at idle and throws a P0300 code with a flashing check engine light. I let the truck sit for 24 hours to see if something would dry out and it would run fine but that didn't work. Changed plugs and wires (was time anyway) and all the plugs on the passenger side were black and fuel fowled. New plugs didn't change anything.

I have a digital temp gauge and can watch the header primaries warm up with it. Driver's side warms up perfectly fine, passenger side however doesn't. Cylinders 2, 6 and 8 do not warm up so I moved the coil from cylinder 4 to cylinder 6 and nothing changed either so I do not think it is coil related.

The air filter didn't look wet but there was a bit of dampness in the bottom of the box. Idle smells very rich and HP Tuners isn't much help either.

Someone please help me. This is my daily driver and I can't drive it.

I am starting to wonder if it is o2 sensor related. In HPT scanner, the driver's side sensor fluctuates but the passenger side is a stagnant 30 and doesn't change. I think I might pop in an old speed density tune and see what happens.

A dead o2 sensor will cause a lot of problems, unplug it first and it should default to like .450-.470mv and the idle will smooth out and the black out the tail pipe will stop.

I will give that a shot first thing tomorrow then. The exhaust doesn't blow out black but it smells very rich. It actually has a hint of white (like moisture burning out the exhaust) but no smell of oil or coolant..

Unplugging the passenger o2 sensor fixed it I think. I noticed my number 8 header primary still didn't heat up like the others did however. But while driving, I can't feel a miss or hesitation or anything. I'm hoping the plug just had a build up of fuel on it that needed to be burned off.

Welp, then replace the o2 sensor and it should be alright then.