you would not want it to go to the intake manifold... you need to make sure that its up stream of the MAF otherwise your introducing un-metered air into the system. Not to mention you have pressure under boost. The only place you would want to install it now is between the air filter and the turbo. But people dont like the possibility of getting oil on the turbo intake so they just vent the catch can.
You will want to check the filter periodically though. they can get oil saturated and get clogged up and then your stuck with no venting again. I think most people just get tubing and do a loop / bend like on a vent for a in the cabin battery box. this still allows for their to be no pressure build up and you don't have to worry about a clogged filter.
2001 ZX3 2.0L Zetec-
Hatch Nation #42
Going through Rebuild See "The TICK Build Thread" for details (http://www.focusfanatics.com/forum/showthread.php?t=289168&referrerid=62897)