The pressure nipple is likely not drilled through, which is good. And no, it will not run if the vent is attached to the nipple because it will not let air in the vent. As I said before, I usually saw it off flush, as I will never use it, and it gets in the way on some motor mounts. You can leave it on though, maybe for resale purposes. If I want pressure feed, I use backplate pressure or a bladder. That would be with no throttle. Tee Dees are more suitable for pressure as they are more of a performance motor.