The nipple is fine as a vacuum source. Your Texas bike has a canister, or is the nipple attached to the resonator under the tank?
See my correction above. I gave you crap advice earlier and whatever's going on with the site kept me from correcting myself. If you use the manifold the signal will always be "on", even when the butterfly is closed. Won't work.
The unit has to feed from the mouth end of the carb or it will feed fuel constantly, even at idle. My bad..