2.5" piping into a 4.5" Cannon muffler - It will be loud and performance will be there..
Get straight through everything.. Good quality like Apexi N1
P.s If u have lots of money go the extractor route (cheap) and cams make a nice lumpy deep n/a grr...(cost a bit)
This was done by a guy in SilviaWA and his car goes hard and sounds even better (speedworkz video mmm)...
In a skyline, never heard of it but why not huh when all these engines seem so interchangable these days..
Good luck, its always interesting