I have a friend with a 600AWHP 2nd Gen GSX with a GT40R.
GT35R, 40R & 42R are basically the largest turbo you can fit on a 4G63.
(Well, the GT42R, for that matter).
Anyways, although it's on an Eclipse, his turbo doesn't have all that bad of lag to it surprisingly. Being DBB, it spools...