A buddie of mine just put a apex N/A N1 muffler on his 240sx with 2 1/4" piping from the cat-back to the muffler, slightly angled out the back. It uses a 30" glasspack as a resonator and sounds stock at idle-4000 at granny throttle, and like a 350z @ 4000rpms-up. and at idle-about 3000rpms @ full throttle, it sounds a little louder than a 350z, then it is Somewhat annoying and loud @ 3500 rpms and up. there was a noticable seat dyno power increase @3500 rpms and up at a slight loss blow 3000 and on par in between. Gtech showed a .4 increase in 1/4 mile time with a 1 mph increase. The totle cost ran right at $450 with tax and labor. Enjoy!

Car specs:
93 Nissan 240sx coupe 5spd
KA24DE w/ removed air box, NGK R plugs, wires, cap and rotor.