I used to live in Lake Tahoe and that was a concern of mine too(different car at the time), if you have fuel injection your cool(you do with your VX)....if you have a carb there are ajustments to be made.

K&N air filter is the way to go!

Oh, maybe if you reboot your computer that might help a bit(disconnect you battery for 20 mins), could'nt hurt....not sure....somebody else can jump in here about that though.