trying to find a good ratio for my yokomoMR4BX

hello everyone: ive been racing an MR4BX yokomo for a wile and ive recently changed to a 10.5 and 84/20 toooo hot! ,79/25 same thing, and now im running 75/24 and the buggy has almost enough pop and top speed ,but its been coming of 160/180 and im looking for a new gear.The car is belt driven so the front and rear pullies are 33 th. and as far as i know the center oneway is geared 15th. both front and rear.the car weighs 3lbs10oz the novak gtb is coming off at about 100deg and the batteries are about the same temp..Anyone out there have any ideas or expirience with this platform.As always thanks in advance.Doug Shelp