I run two on my Chevy Avalanche. I run a Radiant and another, UMD ???. I do catch some oil. Maybe a teaspoon every 500 miles. I run about 10:1 compression, with 88 octane. If a higher compression, then possibly run a catch can.
On the 4.0L, most run the catch can on the rear CCV tube. If oil in the air filter, then its either the rear CCV tube needs upgrade to 97+ or its blocked up with crude. On mine, I used the FlePro rubber gasket. Upgraded to a 93-95 CG valve cover.