The bigger the engine, the more breather you need.
I've gone through a few different configurations(yes, three). If your engine is over 2 liters(mine is 2165cc), you need MORE than that little EMPI thing. It's great to vent both valve covers, but (I think) the 3-4 side gets a whole LOT more oil pumped into it than the 1-2 side.
I use a couple wads of stainless steel Chore Boy pot-scrubber pads in the top of my baffled 2" x 24" breather tube. Yes, it's 2 feet long. It's all about volume and LARGE hose to feed it. It works extremely well. It works so well that it's not connected to my air cleaners any more.
I bought a small Evil Energy breather that has two ports, one from that long breather and the other from the dry sump tank.
In conjunction with the Autocraft dry sump pump, 8 quart tank(6 quarts oil and foam/air space), all the lines, remote filter, thermostat and cooler, it gets a bit complicated.
The biggest help to breather fumes and blue smoke was rebuilding the heads AND replacing the pistons/cylinders and RINGS. The 2nd ring is Total Seal(the early 911 guys do this too). A healthy engine is of paramount importance to minimal vapors.
That Berg breather that Gordon linked? That thing WORKS.