*I Think* it was Flow master, but for sure other muffler/exhaust companies had charts that related and engine size, given performance perameters (HP) & there suggest pipe size for use with that power. I haven't seen it in quite a while.
While I would agree with that pipe size statement, I myself would go up one size. In most cases (that have crossed my path) the next size up never hurt performance. Even more so on a boarder line-ish power level when the question of what size pipe should be used. That's why I did my "Suggested pipe size list." the way I did.
