probably so if you have a cai you don't have to reconnect the drain line thing. I just threaded another hole and bought an npt valve piece for the PVC pipe. Those filtered caps are pretty cheap and replace that little line so i think i'll look into them. btw i dunno but i haven't seen one that's a k&n?
They are PCV valves....long story short, they vent the crank case gase through the valve covers. Normally they connect into the air breather and have a filter. I take it they are not really necessary as you can get different ones. I assume as long as it has a opening to vent and no dirt can get in there all is good. As for the K&N They may be better but seeing what it is and its function I cannot see too much of a performance gain. Looks wise, they look better than having hoses. Hope this helped.
It's not a PCV valve, it's a breather. the idea is similar, but does not function the same way.
The open breather will help keep crankcase pressure down, make it easier on seals, etc, possibly even boost power output (I have no proof). I run them on all my cars and my truck.