As far as I know this was made properly with no defects. I'm not sure if the mileage is better because the car has bugs and squirts at low revs so I'm not sure if the injectors are working properly or the combustion is correct. However, I find that after removing the cat completely and getting a true dual exhaust, the problem is 90% better. The sound is ok. I put short titles, I was looking for a more bassy sound. Although it sounds good. I have a 94 F150 Flareside 5.0 liter 302 engine.