2 inch pipe vs 2 1/4 inch pipe

The way i see it is, exhaust is all about getting burnt gasoline and air from your engine to the atmosphere right? And the bigger the pipe the more cfm it can handle. Now, since this is a stump puller, and not a goddamn datona 500 10k rpm thunder car, you aren't going to be taking advantage of that full cfm shown in my previous post's chart. After milling it around in my head, 2-2 1/4 will be fine. Its kind of a standard size anyway, and summit carries kits.