Errors / Bad Gas / Broken Injectors?

Hello,
Quick rundown on the truck.
My Tundra is a 2000 LTD 4.7L. It has long tube headers and magna flow exhaust, cold air intake, a faulty O2 sensor, shitty steering rack, and a freshly replaced radiator.
All in all it runs good for a 2000 with 300k and no major engine work or adjustments. I use castrol synthetic oil and change it every 5k miles. Its usually still somewhat golden at each change, which blows my mind for this many miles on these rings.

Anywho, I was recently almost on empty and stopped at a local station to get $20 in regular unleaded. Truck ran fine when I pulled into the station. When I left the station, within a half mile, the truck was running horribly, really rough, misfiring, could hardly get it to move. On my way home I got some fuel treatment for water in the fuel. Limped home a few miles to check the OBD2 for code errors. It originally said MAF sensor error, but after clearing and starting over, that code went away and I was left with 4 codes.
General Misfire Error, Cylinder 5 misfire, cylinder 7 misfire, and fuel Too Rich Bank 1. I am wondering if my injectors went bad instead of the possible bad fuel?

Any help would be much appreciated.
It tend to run ok at higher RPM, and like a Harley at low RPM.

 

I'm not THAT familiar with the 4.7L, but something real quick that you could try for free is to see if the coil pack that distributes spark for cylinder 5 also does for cylinder 7. This is how our Sienna was set up. We were getting two cylinders that were throwing misfire codes. On that vehicle, there was a coil pack on three of the six cylinders and from each of those packs was a plug wire that ran to another cylinder. When the pack starts to die, two cylinders were getting intermittent spark (misfires). To verify this, I moved the pack to another location changing it out with one of the others. I then drove it until I got another CEL. For me, the misfire codes went from being cylinders A/B to cylinders C/D. New coil pack sorted it out. About $100.

 

Sounds like bad gas. But that also may be the straw that broke the camels back. I would check the injectors and plugs out just to be safe though.

Did you notice any increases in oil pressure/temp?

This is also a possible reason. Keep an eye out for increased emission and bouncing all over the place at idol. That can be indicative of possible o2 failure.

 

No increase in pressure or temp. As far as I know, the O2 has been bad for a long time. Ha! I feel like an idiot saying that! It gets easily over looked. But to be honest, the truck has run perfectly with only an occasional bad O2 reading, probably something with the wires or connectors. I'm heading out to check plugs, injectors, and possibly try to drain some of the tank.