I'm not sure if they have any aftermarket pipes available for an Indy 500, and if they exist you'd be pretty hard pressed to find any. If you're looking for loud, you could take some of the packing out of your can, although that's pretty much a hack job. If you're looking for more power, there isn't much you can do without going internal. Overall best bang for your buck is a clutch kit. Doesn't give you any more power, but it does make the power delivery more efficient to get the power to the ground better.