last year bought a 00 vmax with 10k with a 4-2-1 Kerker exhaust. i put on Delkevic front header, and rear stock header and put on cobra slip on. I just like the look of dual exhausts(4 pipes). Hear is the results of dyno before and after, i am guessing it's been rejetted with the Kerker exhaust. i did not rejet with cobra ex. Had problem with left rear slip on, only go on 1/8 in. Cobra said i doing something wrong.lol. After reading what i can do to increase hp on a stock motor does not look like i can do much, KN filters,carb syn? :ummm: