The stock air intake is a true CAI and will flow plenty of air. you can mod it if you want, but there is no gain to getting an open element.
A good tune up is the first thing you should do. oil and filter, air filter, fuel filter, plugs, cap and rotor, frant and rear diffs, t case.
Eh okay.
OP I believe your truck should have two breather studs, not one like most older/carbed aftermarket breathers. It is a pain so I just went to my local Ace and picked up a piece of 1"x4" bar stock, 4 nuts to hold the bar, one threaded clip and a new stud. I used one of the old wing nuts from the original breather. It cost me 3 bucks. I had a K&N set up from an old mud truck in my garage, so instead of paying two hundred bucks for a new one I just cleaned/serviced it and stuck in on there. It looks better and performs better than the paper filters. There are a few problems with the original breather, mainly the horrible accordioned intake tube that goes from the fender to the breather. Another power robbing component is the hot air choke inside the inlet neck on the breather. It blocks a huge amount of air and really does nothing until it malfunctions or until the tube falls off of the exhaust manifold. Here are a couple pictures I just snapped, hopefully they will show the little adapter well enough to figure out.
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You might notice that the bottom of my breather is upside down and that is because it was a drop base unit. It won't clear the distributor or MAP sensor mount so I turned it over. Been that way for a couple hundred thousand miles and no issue at all. I clean the filter at the correct intervals and apply the oil correctly. That is the motor as it sits now with over 300k on it.