This ignores the effects of manifold pressure.  The spray bar is restricting the air flow so the manifold pressure will be higher behind the spraybar.  The area 90 degrees to the side may be lower when at full throttle when velocity is highest, but not at low speeds.  Because of this  you basically know what you have with the orifice pointing straight down the manifold, to the side may or may not be lower pressure.  Also toconsider is any effect if the spraybar is off center, which side would be best?