I've seen a few different things knock out one bank of cylinders. The catalyst is a definite possiblity. I've seen that cause the problem many times. The engine control module can cause the same problem, but I've only done a handful of them for that particular issue. The O2 sensor could cause one bank to lean out to the point of cylinder mis-fire, but the odds are it would throw a fault code before there were any drivability issues. I've also seen water in the fuel cause this problem, but that will knock out the left bank, due to the shape of the fuel rail.