What would be the most worthwhile upgrade for the FZ09?

Powerful engine, agile chassis: Yamaha FZ-09 gets praised for that, but criticized for other stock components. As a result, there’s a thriving aftermarket scene with owners arguing over what is the best upgrade to make the bike faster and more fun to ride. Suspension components, exhaust systems, ECU flashes and ergonomic modifications are the common upgrades. The purpose of each of these upgrades is to fix different parts of the bike, whether it’s making it to handle better and have more power or to be more comfortable and less noisy. This is often the debate about which upgrade gives the most bang for the buck, taking into account the cost, difficulty of installation and the amount of difference it will make to the riding experience. It is suggested by some to fix the bike's weak points, and others advocate upgrading the bike's strong points. Often the discussion will speak to how various upgrades play off of each other and will change the character of the bike.