I have run racers edge, cpi, shearer big bores, and shearer small bores......
the big bore out frame shearers put down better times on my 4 mil big cheetah
but on the 7 mil cub the racers edge pipes put down better times.....
cpi pipes didn't do well at all on my bike.....but then again my buddy has cpi small bores on his 4 mil stock cylinder bike and couldn't be happier......