I currently run both valve covers to a T flange, which then connects to my baffled mishimoto catch can, which is open to atmosphere with plenum plugged, and my intake is admin so no nipple on there. Is this a fine way to run it or should I edit some things in my set up? Today I did an oil change with 5-50 to test it out, probably going back to 5-40, I was having excessive blow by come out of the breather so decided to go with heavier oil. I did compression and leak down test, both came back with amazing results so I doubt it’s my rings. Today after the change my dipstick blew out at WOT so either my dipstick was just loose or there was way too much pressure that wasn’t being vented out. I have a 2005 G35 with 138k miles. Full bolt on with some pulley deletes and others being lightweight ones, aftermarket diff with a higher gear ratio pushing about 280-300 to the wheels, stock internals.

 

The t-fitting is restricting you and it can't get enough blowby gas through the single tube. You need a 2in 1large vent out baffled can. You can just drill/tap another fitting onto your existing can if you want.

Blowing the oil dipstick is a classic sign of not enough cfm on your catch can.

EDIT: If there's still not enough cfm then your single out might not be big enough, drill/tap to the next largest size and try again. Or Drill/tap and add a second breather.