I have a 421 cub that had big bore shearer pipes on it. It ran pretty tall gearing with these pipes but if you had to lift off the throttle it would just bog out. Now I have small bores but it seems like it dont have the power to pull long gearing any more but its more forgiving if you let off throttle. So what are your guys thoughts on this, plugs are very clean with the small bores idk if I may be too lean on mains now.