Hi, i own a 2003 YZ450F and i'm planning on buying a slip on. There are 4 that i like and are close to my budget so i need some advise to decide. 1) Yoshimura TRC 2) Pro circuit T-4 3) FMF Titanium Powercore 4) FMF Speed Which one do you think is going to give more power to my bike and on what range?Also do you know which one is lighter? Generally any info on these slip-ons would be appreciated!!