Échappements

On a Milwaukee-Eight, yes. The bike leaves the factory running lean to meet emissions, and a freer-flowing exhaust makes that lean condition worse — more heat, and over time, real engine wear. Slip-ons plus an ECM tune is the standard, safe Stage 1 path. The full reasoning is in the Stage 1 guide.

Yes, if you choose road-designed parts. Reputable slip-ons — Vance & Hines Eliminator, S&S Mk45, the Screamin’ Eagle Street Performance line — are sold E-marked or with road-legal baffles for exactly this reason. Open drag pipes are a different decision entirely and will draw attention at roadside checks.

For most UK daily riders, slip-ons plus a tune. They replace the rear muffler only, keep the catalytic converter on most modern bikes, and give you most of the audible character with a small mid-range bump for a fraction of the cost of a full 2-into-1 system.