Standalone EFI solutions are not without their own issues.
First and foremost the FAST XFI system is nearly double the price of using a factory computer.
Second, tuning with a laptop is not that easy, though the software gets better with each iteration and the latest version of FAST software combined with a wideband O2 sensor allows for a great degree of self tuning. (I have no first hand knowledge of just how good the self tuning is, so take any "self tuning" claims with a grain of salt.)
Not trying to disaude you from going the FAST route, merely trying to lay out the costs and benefits of the decision. I decided to go the Megasuirt route, which has many of the benefits of the FAST system at about 1/2 to 1/3 the cost.
Regards,
Joe Dokes