in the same day we tried t-5's, lrd's, cpi's, and shears on the same bike and actually rode it around..
i ahve a lot of diff pipes laying around here and those were just how they felt to me .. same motor, day, ride..
in my honest opinion on a 421 or 400cc 4 mill stock cylinder motor. the trinity pipes work the best all around. the shear, cpi's will have more top end but in trail and dunning can be a lil tricky..
on MY particular engine with the work thats done to it the motor made 55ft lbs of tq and 80+hp on race fuel. its on alky now and the entire powerband is stronger. sure if it was a "drag" motor i would deff get a set of cpi's or shears or snipers for it ..