Starts at 13-15 af at startup and then gradually goes past 17 at a sitting idle. Is it just because the size of the cam and the valve events?

I read a few threads saying that af would be inaccurate at idle depending on how big the cam is.

If this is the case, how in the heck do I know if I have too much or too little fueling at idle?

I have FAST 36lb injectors and a Racetronix fuel pump.

Thanks for any help!