Your question is just too large. Try using the search button for common questions. Bolt pattern is 5x114 use a website like tirerack.com . There is nothing behind the lower grill inlets unless you put in a TRD CAI. Vinyl is probably cheaper and it is removable. Not yet seen a CF roof cap. You can use a short intake from a TC if you get a MAF adapter, but I think the TRD one made for the xB is nicer. See this thread about speed
http://www.clubxb.com/forums/f65/177...u-pushed-your/
For a low cost mod you could spray paint your engine cover, or peel the a pillar vinyl or get a set of springs and drop it. That is all I got.
P.S.
http://www.merriam-webster.com/dicti...rchangeability