Just out of curiosity... What exactly leads you to believe that "the exhaust cam isnt opening up"? And how did you verify this with the engine off (no oil pressure) and out of the car?
This may help you:
VTEC video - Car Videos on StreetFire
As you can see from the video, the cams don't do anything, they just spin along. At the right RPM range and oil pressure, the VTEC solenoid opens up allowing oil into the appropriate orifices. The pin inside one of the rockers moves to engage the center rocker, then the middle cam lob (high profile) is the one that's doing all the work.
Do you feel a sudden rush of power and more engine noise at 5200 RPM? That's when VTEC is supposed to kick in and its pretty noticeable. Any check engine lights?