How would we describe the 850 stage 4 kit? Pull-the-rope-and-go performance perfection... For starters, we add the patents pending SLP Single Pipe Set to build some serious power and drop 9.6 pounds of unnecessary weight. Next, the torque monster Power Dome™ Head Set creates massive mid-range gains with top-end improvements too. Topping off the horsepower, we include the Performance Edition Porting on your cylinders for a total gain of 16.5 hp peak and 8 hp midrange. Like an orchestra conductor waving his baton to make sweet music, the Flash Tun’R™ with SLP mapping makes sure all kit components are tuned to work in perfect harmony with each other. Lastly, the included Power Shift Clutch Kit™ gets all that extra power from the engine to the track. If you are looking for the ultimate match of performance and consistency, you just found it.