One other cause of a surging idle that may have already been addressed (I didn't read every post of the past 5 pages) is one that afflicts supercharger owners.
After installing your Vortech you may find that the engine won't idle correctly. If you are able to rule out the other causes noted above, you should verify the crankcase is vented properly. This doesn't effect all sc owners the same, but be assured its an annoying problem.
The nipple at the oil filler can suck in air at idle. If this happens air is ingested into the combustion chamber that is not metered by the MAF. An erratic or sticky high idle results. When Vortech first sold their kits they had you run a hose to the filter "area". Now they include bosses so you may run a hose from that nipple to the intake elbow that fastens to the compressor. Since I own an older kit I had to order the updated elbow special.
But it cured my surging idle instantaneously and the car runs like silk (even with my cam)
Hope this helps.
