XRAY - Model racing cars

Hi Paul,
I have recently bought a 17.5 Turn NEMESIS. I am having a problem getting the timing setup correctly. Im running a T2 009 large pulleys, Tekin Rs speed control. I have it all set-up as the following, 21 on the timing boost, turbo set at max and 6 degrees of timing adv. on the end bell.
The issue I'm having right now is at the beginning of the race the car is great good punch and top end. At about the 4 min mark the car starts slowing down. By the end of the race my lap times are about .4 to .5 slower. It loses all of the punch and top end. I check the temp and Im at 165 to 170. Is this to high for this motor? Im also running a fan on the motor. I have tried changing gearing also if I get the temp down then my lap times suffer. Im the only one running this motor combination at this time. There are quite a few people running duo2 with the same speed control. Would I be able to mimic their setup. Any help you can give would be greatly appreciated.
Rick