Black smoke from exhaust

Okay. Do you have a scan tool that we can check for codes? If so, are there any codes?

Next the fouled plugs and black smoke are a result of too much fuel. So if all cylinders on that side are fouled the same the we need to look for things in common on that side that could cause over fueling.

This means we need to monitor o2 sensors on both banks and go from there. Clearly the o2 sensors should reflect the rich condition so we need to confirm this first. Make sure you put new plugs in as well. Thanks

Code P0171(system too lean (Bank 1) and P0300 random misfire. I've changed all the spark plugs, change the fuel injectors, change PCV valve. And mass air flow sensor. I have changed the upstream O2 sensor not too long ago because it through a code that said it was the O2 sensor. I should try changing the downstream sensor?

That is interesting that it is throwing a lean code. Have you checked for a vacuum leak?

Are you able to read the o2 sensors with a scan tool?

If not, let's start with checking for a vacuum leak. Here are a few guides that will flood you with the info about what is happening:

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/engine-black-smoke