I was going to swap my stock air filter for a new one and found about 2 tablespoons of oil and or gear oil in the air box, this doesn't seem to be normal. Plus my oil is only half way up the dipstick. I'm kind of concerned as my trailmaster only has 160 miles on it.
Oil accumulating in the stock airbox is normal, but happens in larger quantity when the crankcase is overfilled.
The intent by the manufacturer of routing the vent to the intake, is so that aerated oil from the crankcase vent will get sucked into the engine's combustion chamber and burned.
I hope you got a UNI Filter instead of new stock airbox.