Z4Ccoupe

Too much knowledge can be a dangerous thing. And I admit I really don't know what I'm doing. But... I plugged in some high dollar Snap-On diagnostic tool and got some interesting info. But I'm not sure what it means. I have had a consistent knock sensor SES warning. With this tool, I noticed that the oxygen sensor reading on one bank was lower than the other bank with the throttle open. Like 660 on one, 630 on the other. In testing sensors it said I had 2 failed EGR sensors. It also said I had 2 failed cat sensors. So what does it mean? Or do you need more information?