On my cosworth there's a Supersprint exhaust system. Its's only 2,5 inch so not the best for big power, but the sound of it really is super. In car you dont have the nasty resonance sound when cruising on the highway at 120km/h (say 3000rpm). My previous cosworth had a Mongoose. It sounded awesome outside, but incar it could be a headache maker..

Dont know if Supersprint sells any 3 inch systems. Just want to give my experience with it.