Those small holes, five of them 1/4" in diameter, bring the total sectional area of those holes up to the same as the 1.5"ID header pipe. This makes the bike run better than it did in previous restricted form, but makes it 7 decibels louder. At idle. 5 feet away. Here’s a video courtesy of my friend’s willingness to beat the shit out of the bike to see if it’s any better.