I believe you need to unplug it for anything containing more than 10% ethanol. If you're running the 10% ethanol that most places have, you should be fine to leave it plugged in.
When unplugged, it just adds more fuel across the board. Unless you know it's running lean with the 10%, I'd leave it plugged in.
2006 Arctic Cat SnoPro 440/700 EFI
1998 Arctic Cat ZR 600 EFI Custom
1996 Ski-Doo FormulaIII 600
A mountain lion roaming the prairie found a bull, killed it and ate the entire bull. With a heavy belly, unable to walk, the lion laid in the tall grass moaning and roaring. Soon a hunter, attracted by the roaring, shot and killed the lion.
Moral: When you're full of bull, keep your mouth shut!