I use a ratio right, mixed a gal. of 110 leaded sunday. To ride the 04 cr144 and 06 cr125 back to back, to make a decission on which 1 I,m selling. I was thinking the 144 at 1st, I rode it with the 03 KX 125 HGS BUD pipe, then the 06. Then put the PC pipe on the 144, huge diff. in performance, the PC hits quicker, then pulls very hard, a eye blurring rush of power. The KX pipe on the 06, ran leaner than the stock pipe, I was shocked by the lowend snap, harder hit the pulling much harder with 2,000 more rmp, pulling the whole way. That same pipe on the 144, ran flat, but had great mid pull with 2k plus more rpm. The stroker crank slows response down, so a pc pipe with better snap is a good fit for the track. PS alot of hours fabing the kx pipe to work on a cr.