You can try simple cosmetic upgrades like the Mazdaspeed engine oil cap or a radiator cap. Try painting the mazda emblem on the IC shroud a different color. When you do start doing performance upgrades, see what colors you want to use with what colors are available on certain parts. Strut bars, recirc hose, vacuum hose, boost tubes, CIA, you can get them in different colors. See what your options are for the parts you want and have at it.