Your factory Blow off Valve (surge valve) that came stock on your vehicle vents intake pressure back into the turbo's compressor housing. In stock form, it is very hard to hear the "woosh" or "psssft" when you left off the gas, because the air vents right back in.
The EVM changes the direction on the pressurized air to the atmosphere, and allows you (and everyone else) to hear it. It sounds great!
Longer bolts are included in the kit. Fits Neon SRT-4, Caliber SRT-4, and Genesis Coupe 2.0 turbo.