is your tach working?? check that too as the same happened to me. i converted my ef to have b18c also. one day vtec worky, the next it didnt. i realised that my tacho didnt work then noticed that vtec wasnt engaging.

vtec needs rpm signal to engage, on top of whats already been mentioned.

hope that helps mate.

ps, where the hell are you guys getting a bottle of vtec for $1.95 im paying at least twice as much as that!!!