My stock airbox didn't even really connect to the tube. It was actually behind the air filter, before the air was filtered, and wasn't even really connected to the box, more than it pressed up against it. The old intake I had didn't have a sot to put the breather tube in, so I just popped a small filter on it, and I assume it'd be okay, as long as you keep the inlet away from water. The old intake box goes like this:
X = Breather tube
---- = Air path
O = Filter
Outside air-----------------X----O------Engine/hoses
The hoses right next to the carb always have a spot to go into the intake tube, so those solve themselves, right next to the sensor.