I've heard that there was a recall on the crankcase breather or something along those lines that caused oil to build up in your air box.
Changing over to a new Unifilter I noticed a pool of oil in mine.
My machine is well out of warranty (2016), so should I contact CFMoto?

[2015 Z Force 800 53/Trail EPS]

You can try but I wouldn't expect much. I thought it was the 500s that had the recall.

I think this is what I'm looking for.

https://cfmoto.procorepower.com/0gra-0141a0-crankcase-breather-kit-cfmoto/

So I have a 2016 I bought in 2017 and cfmoto Canada just warrantied this issue for me. The fix was changing something on the side of the engine and rerouting the Crankcase vent hose to it, it was a pretty big job. There's a recall for it, I could probably dig it up if someone wanted

I ended up getting the recall fix kit from my dealer and doing it myself a few years ago. It wasn't too hard to do. I've since sold that 2017 400 and my 21 Zforce.
That 400 was a good quad. It did everything I asked of it. It just was plagued with cooling issues and waterpump seal problems.