engine basics 101. better flowing exhaust=power+economy. at the same time, bigger isn't always better because fluid dynamics shows that as you increase diameter of a pipe, speed goes down. decrease pipe size speed goes up. key is finding the balancing point where you have a small enough exhaust to keep the velocity up and get gasses out but not so small as to be a restriction.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"