Originally Posted by Kai
The intake manifold is a minor problem, thanks to the Skunk2 manifold and similar R copies made for the P72 bolt pattern.
The GS-R trans is also a minor inconvenience, as you can drop in a number of LSD's and change the final drive gear (ex: a JDM Type R 4.75) if you like.
Exactly. He asked if the R engines were less customizable. Those two problems are the only barriers to tuning in which the GSR costs more to modify than the R.