That is the high speed needle where the fuel tubing connects to the carb from the tank. 2.5 turns out for that needle seems a little low.

I am not completely aware of what type engine Associated use on the RTR car (whether it is barrel or slide type carb or the number of needles on it).

If it is a barrel carb (the throttle lever rotates instead if sliding in and out) it is possible that it is only a single needle carb in which case 2.5 turns could possibly be right.

Where the throttle rod connects to the carb check to see if there is another needle at that point (not the little black one with a spring on it. That is the idle screw). If so then try adjusting the carb as I pointed out above.