I was hopping for some input, I have a 08 525 IRS with 4.1 FMF slip on, JD jetting kit and cut holes in my airbox, I feel it runs very good and dont really need any more power, its just a matter of wanting it. So whats your thought on big bore kits vs. NOS? I am leaning towards the 570 BB from thumper racing, but I have heard alot about NOS and it is cheaper.