Lots! I’ve had this home-made catch can on my PCV line for quite a while now, and I’ve found that I don’t really need to seafoam the intake every few thousand miles to calm the idle back down, and overall it seems to run a bit smoother day to day.

This is the typical 3-400 miles worth of catching, just wanted to share (I drained it today). Gross stuff, looks like water/oil and smells like rich lawnmower exhaust - there’s a reason I don’t do like some OEMs and drain this crap back to the crankcase...

Yes, my catch can is a modified air-line dryer with a needle valve grafted on the bottom for tool-free draining. Lines to the manifold/PCV valve are steel lines I bent up, with rubber hose as couplings.