Did somebody really say high performance and Harley together, lol
20% gains from an exhaust? Dyno sheets?
Actually, the damn things are tuned so lean to make the EPA happy that pipes and a carb rejet could actually net you 20% on the pre-fuel injection models.
The fuelies almost woke up that much with the Screaming Eagle Street Tuners, which is why almost everyone bought them. Which is why the EPA just nailed Harley on them. Oops.