Npp
Riley.... I believe the NPP exhaust system is the dual mode exhaust that comes standard on the Z06. Under certain conditions, ie: 3500 rpm and some others, a valve opens allowing an almost straight thru exhast. There are aftermarket switches available that will allow you to change to either mode with a switch. This switch has been referred to as the 'Man Switch'. I like it. I feel that there are times I would like to go a little more unoticed and then again, I love the sound of the wide open. Most oftern, I'm on the LOUD position.
I had Corsas installed on my Grandsport when Lingenfelter did their magic on it and it sounded great! But.... there is a caveat here.... it was a little more than loud going through town, even at slow speeds. I love the new system on my Z06 because I can have it both ways!
Terry