[jhautz]

Your supposed to gear a higher kv motor down.... not up! Go back to your original gearing that you ran with the 9xl and tell me how it feels. Gearing the 9XL up as high as you geared the Neu 1512 would cause it to overheat in minutes. The fact that you are running it at only 165 is a testament to the Neu. Also the 9xl will feel less torquey at that gearing.

If you not getting more speed out of it at the same gearing you for sure have something wrong with the motor. At the same gear ratio the higher KV motor on the same power source should run at a higher speed.

Gearing them the same should give you a better view of the relative power of the 2 motors.

EDIT:
if you get 35mph on you 9xl geared at 14/46 and you are looking for the same speed/power only coolier temps you would need to gear the Neu 1512/1.5Y down (very slightly). Gearing up will naturally give you more top end and less low end.