[MPaulHolmes]

I think you are right. It's not the pot. 3.33v was the absolute bare minimum that it had to be for 0 throttle. Assuming the resistors were absolutely perfect, and assuming that you just shorted across the throttle to guarantee 0 Ohms, the voltage at the microcontroller would have been:
4.7k/(2k+4.7k) * 5v = 3.51v.

I said 3.33v since there's built-in dead throttle. Anything in the 3.33v to 3.51v does nothing. Now, to get 3.03v, assuming R10 was 4.7k:

4.7k/(R8 + 4.7k) * 5v = 3.03v
So that R8 = 3.06k.

So, you may have used a 2% tolerance 3k resistor instead of a 2k resistor for R8.

I just noticed from the picture that R6 is a 4.7k 5% tolerance resistor from the color code. I don't see R8 anywhere though. Can you include a picture of that one too?