I noticed when I changed the air filter oil standing in the bottom of the box. It's almost clear no smell and thin. Almost like compressor oil. Is this supposed to be there to help with filtering? There was about a 1/2 cup that I poured out.
Change PCV valve and see what happens. That oil looks way too clean...that is accumulating on the unfiltered air side of your filter, so that oil should have some dirt and debris that normally gathers there.
I noticed also that there was some kind of what looked like yellowish grease in the pleats of the intake hose. I really have no idea what it is or how it got there but like I said it's almost clear and thin. Way thinner than engine oil.
I took out the PVC valve and it seems to be in good shape.
There are a lot of problems with the standard air filters nowadays and I still don't know why you are using them because they are almost useless, they are too weak to deal with the high level of pollution in the cities and towns and a lot of harmful substances which are consisting in the air like CO2 get into your car and the air filter helps with nothing. I read a post on Do Ozone Generators Really Work for Hunting - Damage Control 911 about the ozone generator and after that, I immediately bought one of this and during one year I had no problems with it, and more it works much better than the standard air filter.
Post #5 should vote for Trump, the info given there is as good as injecting bleach to stop covid. No air filter on earth will stop CO2 from getting through it and ozone is one of the major causes of rot to underhood rubber parts over time.