How big of Intercooler piping?

[Forced Fed]

From what I have researched (can't find a whole lot) people who have upgraded to the GT25R haven't seen significant amounts more of turbo lag.

Also read a little about a guy who had a Wicked Racing turbo kit on his FS-T that made 255+ hp on a 16g. However I couldn't find much out on his kit as Wicked Racing doesn't exist anymore and he has since sold his sled.

Edit - I'm open to suggestions on turbos, its just the stock turbo is way to small for my liking...