And I'll tell you it's not possible for a VN to run slower than 16 flat : )
IF it does your car is stuffed, or you're getting wheelspin, simple as that. They ran 15.6 all day everyday with the crapy factory tires when new and there is no possible way they were doing full throttle launches without wheelspin on those tires.
Mine only has the VS CAI, The throttle body and elbow has been fairly well worked over, the throttle body shaft is very thin, good edge on the butterfly all the ridges in the throttle body are gone etc, normal stuff. Plus a Home made memcal which would make me alot more power that it does if my exhaust wasn't restricting me. But most important of all is fixing the throttle body to open fully. Exhaust and everything else is stock. There's a video of me doing a 0-100 run in 7.16 around here somewhere but I have gone under 7 seconds quite a few times since then. It runs about 15.55 with the stock memcal, I'll bet you I can drive any decent not seriously broken VN to a sub 16 second 1/4 after a couple hours doing those few simple mods, for that matter a VP or VR too