Stage 1: Intended for motorcycles with a stock engine using the stock airbox, air filter and stock pipe. Stage 1 kits are fully adjustable to allow the use of a well designed aftermarket pipes and stock replacement air filters like K&N. Stage 1 kits are designed to improve throttle response and driveability and in most cases power increases of approximately 5% throughout the entire power range can be achieved
Stage 2: Intended for motorcycles with a stock or mildly tuned engine using a well designed aftermarket pipe with a modified airbox and a stock replacement air filter. Stage 2 kits are designed for applications where individual filters cannot be installed and for applications where airbox modification improves the engine's performance. In most cases power increases of approximately 8% can be achieved
Installed the kit in my '08 shadow 750 in about an hour. Added a little noticeable power throughout. Smoother idle and a little faster rev. Well put together kit with the mixture screw adjustment tool, new needle and spring. But I have one gripe, and that is the instructions are vague and not so helpful, but its a straight forward and easy install.