Your car is so rad. Are those wheels also called RK? If so, very light weight. However, check for cracks, as all my 18x8's had hairline cracks in the ends of the spokes into the barrels. Was so so sad when I found those.
Have you ever considered a newer generation turbo? They likely would flow as much as the HX40 and come online much earlier. Or is that how shit gets broken? lol