also, the "AMS bov upgrade" is just an OEM bov - don't buy into the marketing. I'm a bit biased towards AMS fanboy-ism, so it really irks me that they go about advertising stuff like this. don't be fooled - if you find an OEM one cheaper elsewhere, go for it
if you're looking for more ideas on mods, my Evo X thread might help
http://www.evoxforums.com/forums/showthread.php?t=57947