You probably don't have it set to run OC all the time. You have to disable the power saving features in the BIOS to get it to run at 4.3 all the time. It drops the multiplier down when you are not using the CPU much. Some people like it the way you have it set.
Generally, you can get a higher OC by turning off those power saving features, at the expense of using more power all the time.
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