Put this on our 4 cylinder BMW race car after a failed sound check at Thunder Hill. Just a straight pipe and that muffler on the 4-banger is a great harsh sound that you can hear compared to other cars but not too loud. We passed the sound check at Laguna Seca, one of the toughest tracks in the world. I would imagine it would be very quiet with a cat or a resonator. The word "turbo" is a bit misleading.