ghosthunter, so far here's what we got from the dealer. regarding lean-rich mixture...

"at minimal vacuum (2inHg) the mixture po is always correct at any state of your engine, be it idle or high speed or anywhere in between. that means its neither rich nor lean. lagi lang pong tama as shown during actual installation kasi the 2 inHg is maintained no matter how high/low the rev speed is.

Look at it the other way, (without the device) you have a high reading of 17-21 inHg at idle speed and varies from 17 - 35 inHg (35 inHg occurs at engine breaking at high speeds) depending on the state of your engine. Meaning at any instance of idle state, you have very, very, very rich mixture! "

i hope you or other experts here could enlighten me on this one. coz i really don't know if the 2inHg is really a good figure.
i just saw the actual demo when they measured the vacuum reading on my car before (17.5inHg) and after(2inHg) the installation.

thanks for the help...