Your carb settings need to be.....
adjusted. Tell us how many turns you have on the high speed needle. If I'm not mistaken the HPI has only one needle which is the high speed needle. It is better to run rich than lean especially on new motors. Make sure that before you do any adjustments to the carb, the motor has some heat to it already. I mean don't adjust with a cold engine. Warm it up for a couple of minutes then do the adjustments. Start rich, run a couple of rounds then checking for acceleration(if it is bogging), bring the car back in and check the head temp. Lean out the carb 1/8 turn at a time on the HPI carb that would be a click at a time. Repeat this procedure until you are satisfied with the acceleration and make sure that the temperature is not too high. My friend has the same car as yours and I gave him an OS carb from one of my old motors and the thing was flying. I just recently modded the same motor for him with some polishing and mild porting. Amazing results, it really made a difference.