GFB 04-10 WRX/STI 3 Piece Under-Drive Pulley Kit w/ Belts (Crank Alternator & Power Steering)

If you're looking to make your 2002-2007 Subaru Impreza feel more responsive, especially when you're digging into the throttle, this 3-piece underdrive pulley kit from Go Fast Bits is a solid option. It targets the rotating mass in your engine, which can sap power as it spins up. By reducing this inertia, the engine can rev more freely, giving you that sharper throttle response and a more eager feel when you accelerate.

These pulleys are machined from a single billet of 6061-T6 aluminum, which keeps them lightweight. The kit includes pulleys for the crankshaft, alternator, and power steering, along with the necessary drive belts. The underdrive design also slightly slows down the accessories, which can free up a bit more power at higher RPMs without negatively impacting how those accessories function. This is a bolt-on performance improvement that doesn't require any other modifications or tuning to work.