cooling pipe, just to see...

[BrianG]

I agree with Squee. Adding that much cooling is good and all, but you are addressing the symptom, not the problem. If you want high speed, increase the voltage until you get to ~37kprm motor speed. If you are already that close, them maybe a different/larger/more efficient motor is in order. Overgearing is not good for the motor or the ESC. It pulls more current than it can safely, and will heat up excessively (as you've seen) and decrease its life.

Now, with the right motor/gearing/voltage combo, that sink will help reduce temps from normal to a cooler amount. Where did you get that by the way? It looks nice and allows directed airflow where it is needed while not looking ghetto.