I’m coming close to buying a cat back. Most are 3 inches but they taper down to 2.5 inches. What good is having a 3 inch exhaust if it has a 2.5 inch bottle neck? And yet, manufacturers, like Cobb, have the dyno charts to back up their claims of improved performance. I’ve read that to big of a pipe will rob you of low-end power. Is that true?