Well I've been doing this for a long time and I can attest to the fact that a properly tuned bow WILL shoot your broadheads to the same point of impact as your field tips provided the broadheads are installed true to the axis of the arrow. One of the main reasons besides improper bow tuning is having the face of the arrow insert not square to the shaft. Another problem is broadheads with a crooked ferrule. The easiest way to check this is to place the arrow on a V block and spin it watching the tip of the broadhead. (its nice to have something like a box with a spot on it as a reference point). The tip wobbles around the spot then its out of line.
There are plenty of videos on bow tuning on Youtube and read the stickies at the top of this forum.. Its not rocket science and its easy to do.