People put cardboard over half the radiator when they have an upgraded cooling system and the car won't get up to operating temp in cooler weather. It won't help gas mileage any.

As Emmino stated, VTEC is either functional, or not. There is no "harder hit" or anything like that. Anyone who tells you there is, is full of shit. VTEC can SEEM to be more aggressive when you change the engagement point because the disparity between the two cam profiles is larger, but the performance will remain the same, you just may be able to get a little more midrange performance by lowering the engagement point when tuned on a dyno.