an x-brace is a great way to increase your handling while protecting your oil pan at the same time
http://yhst-59326584023620.stores.ya...mw-xbrace.html leatherz.com has a pretty nice armrest for a good price
http://leatherz.com/Merchant5/mercha...de=Z3_Armrests as far as engine performance goes, there's not a whole lot you can do on the cheap unfortunately