slightly higher performance, couple of hp only because it can decrease the intake charge with the larger core, and you don't have to worry about heat soak that a top mount gets.
I honestly have no idea where this was bought from. Andy gave me this when I bought his RS from him. So I'm pretty sure it will bolt right up to my '02RS.
There's some Labels on some of the parts..."X2 Racing"...I think...gotta check to make sure.