too hot only affecting mid range?

[auto2]

LSP with 8XL and 9920. 2 5000Mah batterys wired in series.reciever pack

after 3-4 minutes I loose all mid range. still have full throttle and full speed. Let it sit for a minute and it is OK .
9920 is 110 at fan and 160 at capacators
motor got to 160 after about 10 laps with cool down minutes. no fan on motor or heat sink. geared 13/44

like the throttle goes from 0 to 10 and I have nothing from 3 to 8 after a few minutes.