if you want to take the economical route of customizing your car, it is going to be difficult. even if you get a generic muffler just for ur car, our cars exhaust are axle-backs, and thus the muffler shop is going to have to add a pipe in there, thus making it a custom exhaust. i recommend you get TRD
or tanabe super racing medallion. as for springs, you can get used springs around here, they pop up once in a while so when you see one you should hop on that. either that or teins go for a good price on ebay. i got my TRD
springs for 130 shipped used for about 2k miles. as for rims, wheelmax has good rim and tire packages but ive heard bad things about the tires they give you as well as their service.