15 is off the crankcase....case ventilation,top of the motor.
16 is tank ventilation...to the pukecan/breather of your choice.
Here's a pic of a pretty much bullet proof scavenge side routing to your thermostat/cooler......it misses all the goodies, but ya gotta go back to go forward
I've never seen a 3.6L case and am assuming the scavegne line comes out about the same place as the ealier motors.