Cost difference, thats the key thing. I can mod my v6 to compete with GT's for just the MSRP cost difference, nevermind the insurance difference. (at least in the straight line)
and yes it was a 350z.
you have to watch the polishing, if you polish the ports you loose your gas mileage. you want to semi polish, or no polishing at all to keep up your gas mileage.
A bowl blend and porting will work.