Battery location and intake how-to's are on ths page
http://www.240sxtech.com/ not to mention all over the internet.
That big nonsense in front of the BMC is the PAIRC system (emissions crap), you don't actually need it at all (s14's dont have it), but you can't just "remove" it either, w/o plugging a few things. Read up on it.
Near as I can tell, it's going to be a whole lot of work to not actually make anything run any better, and may make things run worse, esp if you don't get all the vac and pairc stuff dealt with correctly. If you're going to trunk the battery anyways that's one thing. But I wouldn't do it JUST to do tamper with the intake. Even if you are trunk'ing the batt anyways, I still wouldn't bother messing with the intake.
Of course it's your car and you can do as you please with it. Just sayin there's no real reason to do it. Unless your reason is "because I want to", in which case that's a perfectly good reason
