I am just importing an LS400 right now from Japan, and it says that it comes with a catback exhaust. In standard form (1989 LS400) are the cats located just after the dumps? Meaning, if i wanted to put on extractors, i would need to do a little custom work on the cats to fit them down just before the X pipe.
Also, do you beleive a "long x pipe" would be better then a "short x pipe". meaning, over the length of the y+pipe+y to make one really long x, compared to just a quick x before the exhausts split again...
hope i made sense