Try a different choke, like the factory full choke and see if that too shoots right, while you're at it try a field load too with each choke. That test will tell you what to do next - change the choke tube, change the barrel, or new gun...
Also make sure the barrel if fully seated in the receiver, and the mag cap is tight - that can play havoc on your patterns.
I had a Mossberg 500 that shot 4 inches left and 2-3 inches low regardless of the choke, and like you the fiber optic sights I affixed to the rib couldn't overcome the issue. So I ended up with a new Winchester 1300 to fix the problem.