as already said, it's perfectly normal. The computer has some parameters it has to learn per driver. When the power is diconnected for awhile, it allows those learned parameters to be forgotten. The neat part about it, is for the next couple of days, the computer will advance the timing and not be so quick to engauge the emissions programming giving you more power.
01 WS6/ Several strategically placed japanese imported chrome stickers, (good for about 30 hp gain). Half of them are placed hidden on the inderside of the body panels for that sleeper effect.
My cars & related stuff http://www.mobius1.net/gallery/