Chico is correct, on one thing, you sound a little optimistic, I would guess that you are probably pushing 250 to 260 FWHP (remember stock GTP`s run around 190 FWHP wich is not too shabby to begin with, now if that Z is manual then I would say that it really depends how good of a driver your friend is (proper launch and so on) but as far as 1/4 mile times, I think that chico might be understimating the GTP as I have seen stock GTP`s pulling high 14`s, with your mods (and assuming that you are not getting any KR) I wouldn`t be surpised if you are mid to low 14 and maybe a high 13, depending on your launch, but it would definatelly be a close race.