Higher kv vs. taller gearing

My mamba has holes through the case with 25mm pusher/ puller fans and a 30mm fan on the heatsink. When I killed my 7xl, it was geared for about 48mph, and the mamba still didnt get over 90ish after 7-8 minutes of running. Thats what made me think this car has more speed in it. But maybe it doesnt without a higher efficiency motor or higher voltage.