Return to sump is only suitable for a race car. On a road car the can fills with water and emulsified oil which is best kept out of the sump. Some people are confusing the vent with the sump return. On a baffled can the oil is collected in the can & won't spray on the road from the vent pipe & won't kill motorcyclists.

 

thats only cause its mixing with condensation when left in the tin. you ever seen the Crawford performance catch can its bonkers as coolant circulates around the tin to prevent condensation forming and mixing with oil

i went with the other US way, the air oil separator that fits onto the oil cap.
http://i5.photobucket.com/albums/y18...ps1a9a369c.jpg

 

The crawford performance one - not cheap
http://www.hptmotorsports.com/subaru...ti-s0714b.html

 

My setup used a kind of oneway valve in the cap, so it would vent but not suck if that makes sense. So any crank case pressure would be vented, the oil collected and returned to the sump.

My catch can is the black thing with the two red caps on, top right. The one next to it was the header. 2 x -12 fittings for the breathers and a -6 return