Idk about Xi fitment but for me I'm running a 12.5mm spacer up front, and planning on getting a 20mm for the rear.
So my setup will be:
18 x 8 et7.5 (et20 - 12.5mm spacer)
18 x 9 et2 (et22 - 20mm spacer)
Maxed out front and rear on Kw V2