Van running rich

Do you have multiple cylinder misfire codes or just missing on different cylinders but consistently on those cylinders?

Here is a guide that will help with misfires:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Random misfire codes just means that each cylinder that is misfiring is not consistent on each power stroke of the engine for that cylinder.

So the ECM determines it is misfiring because it is not seeing an acceleration of the crank shaft when it fires that plug. So it assumes is misfired. The fact that the o2 sensors are showing rich either means we have weak or no spark at times or too much fuel.

I would start with checking the fuel pressure while the engine is running and misfiring and then shut the engine off and see how long it holds the pressure.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

You may have leaking injectors causing the air fuel to be off and misfiring.

Also, I assume you have replaced the plugs and other ignition components? If so, what have you replaced already?

Let's start with this and go from there. Thanks