You have to make a really aggressive primary lobe to mess up the idle with a VTEC cam. If you think about it, the highest RPM they will ever have to make power up to is about 6000 or so and then the VTEC lobes take over.

Basically this flat spot is a symptom of having VTEC lobes that start making power at an RPM higher than the stock 4800 RPM switchover. The motor stumbles a bit before you hit the meat of the VTEC powerband.

If you don't want a really agressive cam I would suggest (in order of increasing price): ITR cams, skunk2 Stage 1, or Toda Spec A. Just be sure to take care of the typical i/h/e first.