So I Will weigh in here even though my advice is going to completely buck the trend of what others are recommending

currently you have your engine quite choked back with both pipe and insert, reducing the engines overall operating efficiency and dramatically educing its potential power both by insert size and pipe/header choice... From that engines full power capacity you are down roughly 35% which in turn results in you using more fuel not less fuel

My crazy sounding advice is to ditch the 41021 manifold, swap to a 41001 and run a 8 mm carb insert ! Even better swap over to a 9886 tuned pipe, the 9901 is a 3 chamber that restricts flow and forces the engine to work harder to breath, the 9886 is a 2 chamber and operates more efficiently... The end result of this is your engine is going to make a whole pile more power and operate much more efficiently , you will clear jumps easier, you will be able to run the track using far less trigger input and most likely end up with better mileage... IMO small carb inserts are not the answer, they end up just choking back the engines power too much and hurting overall operating efficiency more then anything else...

A small carb insert however can be beneficial in some cases on a smaller low speed track where you want to increase throttle low RPM throttle response and will not notice the loss of power and RPM...But on a big track the small insert is going to work against you !