I have not posted on here for a long long time, as I gave the 35 to my wife about an year ago, so forgive me for coming out of left field. I am an interested party here, however would like a little more information.
The supercharger kit was bought for $12,500, do you have receipts? Was the system new when purchased? What power did you make with this kit? Were there any other modifications made to the car to achieve this? If you are planning on letting the supercharger kit go with the car in 13 days, why are you selling? If you are not getting anymore for the car with it, why not lower the price of the kit so you get a sale?
My hesitation is that the same second hand set up can be had from G35driver.com and with the dollar the way it is, 8k is not as attractive.