The stock handlebars that come with a Sportster 883 have some rise from where they meet the clamp. The bars also sweep back toward the rider. For some riders this is comforting, but others may have a different comfort zone. Flat bars, also referred to as drag-bars, shift the controls lower and more forward, which puts weight over the front wheel. This is a good position for cornering performance and better aerodynamics since the rider can tuck down at high speeds. Some riders may find that they can ride more effectively with higher bars or wider ones, and the best performance here is the shape that feels good mile after mile.
Replacing the stock rear shocks with a pair of tunable aftermarket shocks is a good upgrade. A spring and damper unit can offer different spring rates and a lighter weight billet damper-body with multiple positions of adjustable rebound damping. This allows a user to dial the performance of the shock to suit a specific rider weight and riding style. At the same time the rear shocks are swapped out, it is worth replacing the stock fork springs with a pair of progressively wound springs, especially since it is not a costly upgrade.
The stock exhaust system sounds somewhat conservative because it has a lot of baffling to keep noise levels lower. This sound-reducing material also makes the exhaust weigh more and keeps the engine more restricted. By replacing the exhaust with a stainless steel or aluminum system, the bike weighs less and the engine uncorks, allowing better flow of the exhaust gasses. This extra flow creates more horsepower and torque, and the sound of the de-restricted pipe is something most Harley owners can appreciate.