There is two profiles on both the intake and exhaust, this is the same for atleast the performance vtec engines, some just have vtec on the intake cam.
If I went down the dactivation method I would only be able to use one cam profile for the whole operating RPM of the engine of 8800rpm, of course the reason why honda went with VTEC is that they get utilise two ideal profiles for such a vast rev range. If I went with one that favours upper rpm flow then low rpm economy would suffer, if I went with one that favours low rpm torque then the engine would feel like it runs out of puff at the higher rev range, the answer then would be to go with the economy cam profile and run huge amounts of boost, possibly as high as 20-25 PSI from a rotrex unit to give a more linear torque curve and retain my 300-350bhp
Audi run their dactivation system by trapping exhaust gases in the two non operating cylinders, this overcomes the pumping losses in the now 'dead' cylinders but they have a precise system that can operate quick enough and at a specific time to trap the gases, if you ran a vacuum you would, over time, draw oil and gases up from the crankcase which is not a good idea! How I could specifically operate the VTEC at the required moment is still up for debate....