Just check mine and the end cap was in place. I did find something that I was not expecting. This yellow white oil mess. Is this from the oil in foam around the filter?

That looks discusting!  I sure hope that isn't a major issue.

[2015 Z Force 800 53/Trail EPS]

Just check mine and the end cap was in place. I did find something that I was not expecting. This yellow white oil mess. Is this from the oil in foam around the filter?

No oil on that little prefilter. That is from the engine crankcase vent tube and/or some water intrusion. If that little prefilter on the end of the intake tube behind the seat gets too plugged up, it will cause great vacuum on the airbox, and that pulls really hard on the vent tube which can pull oil from the crankcase. But..there also looks to be water in there too. Have you had her in any "tire-deep" water lately?

Looks like milky blow by from the crankcase. Not good. Check your engine oil and make sure it's not milky.

I have only had it out once. I just bought it new there is 90 miles on the machine. Not in any mud deep crazy mud did have a stream crossing. The filter looked clean. Checked dip stick and oil looks fine. The foam of the filter looks like it has oil on it (see picture). Everything else in the filter box looked fine. I guess I better find that little pre filter you mention.

[2015 Z Force 800 53/Trail EPS]

I have only had it out once. I just bought it new there is 90 miles on the machine. Not in any mud deep crazy mud did have a stream crossing. The filter looked clean. Checked dip stick and oil looks fine. The foam of the filter looks like it has oil on it (see picture). Everything else in the filter box looked fine. I guess I better find that little pre filter you mention.

Just take the grill off between the seats. Its at the top of the air intake tube. When I did my cold air intake mod, I left it off.

The service manual   also states that the oil level may be too high. I think I am going to change the oil and make sure I put the correct amount in. The dealer may have put too much in. The level seems high on the dip stick. I will check the pre filter tomorrow. Thanks for the advice.