Anybody know how to make this bus go any faster. I've been looking for parts all over but I'm ignorant in this area.

Here's some of what I have come across.
A NISSAN HARDBODY (D21) AND PATHFINDER (WD21) FAQ to get you started: http://www.off-road.com/nissan/ref01.html
You didn't mention your Model Year, but may find some upgrades here:
Intake [POP-Charger Air Filter] http://www.courtesyparts.com/secondtier_r50.html
[HKS Super Mega Flow ] http://www.racerwheel.com/hks-1504-sn02us.html

Exhaust [Thorley Headers] http://www.thorleyheaders.com/nissan_headers.html
[Pacesetter Headers] http://www.autopartsauthority.com/headers/nissan~pathfinder~headers~pacesetter~parts.html
[HKS Pathfinder Sport Exhaust] http://www.autosportz.com/exhaust_hks_nissan.htm

Camshaft [JWT] http://jimwolftechnology.com/customer_results.asp

Front end components http://www.fly-n-hi.com/nissan.html
Suspension http://www.autocarparts.com/cars/Nissan/Pathfinder/ALL/Suspension/ALL/
also Rancho has an application for Pathy http://www.gorancho.com/RanchoDefault.htm
Locking Hubs [Warn] http://www.warn.com/truck/hubs/hubs.shtml
[SuperWinch] http://www.superwinch.com/products/hubs/
[MileMarker] http://milemarker.com/hubs.html

An ongoing Project Pathfinder at NissanPerformanceMag.com http://www.nissanperformancemag.com/projects/pathfinder.php
Also checkout, "Why some modifications increase bottom end power and some increase top end power? " http://www.nissanperformancemag.com/september02/ask_sarah/

Will post more as I find 'em. RC