Yeah, my Mishimoto is a bit thicker than his koyo, esp with the factory fan shroud that I have on mine.
I can't even fit the stock overflow...been living with a tiny overflow that is designed for FMIC kits that's just a few oz too small for the amount of expansion in my system
I have a mishimoto overflow cylinder that is larger, but I don't have a great place to mount that either due to the smaller and more-cramped GC engine bay, but I guess I have to revisit that and maybe figure out how to mount it on the passenger side of the car where there's more room...
A battery relocation would also solve most RSTi engine bay space issues =)
Thanks,
-- Dave