2003 Santa Fe with engine code 300, 303, 306

Hi guys. I have replaced sparks, wires, coils, and injectors. I still have these codes; yes I erased them. Through this I have looked at the hoses and not found any leaks. And I don't believe of any cracks in the manifold. On LT FTRM1 at -2.3% and 10.2% for LT FTRM2. So does bank 2 have the 2, 4, and 6 cylinders in them? Why are cyl 3 and 6 have codes 303 and 306 in banks 1 and 2? So other than the manifold or cracked hoses, what other things should I look at? Thanks so much....Doug