P0420 and P0430 code. Replaced both O2 sensors. Do I have to clear the codes?

Yes, codes must be cleared.

P0420 and P0430 pertain to bank one and bank two catalyst inefficiency. This means that the 4 oxygen sensors -- yes, 4 -- 1 before each converter and 1 after each converter work in tandem to measure exhaust gases to monitor the effectiveness of the catalytic converter and adjust fuel delivery to the engine and air mixture as well. You could have an engine processor software issue. You could still have sensor issues -- there are 4, not "both" meaning 2. You could have problems with both catalytic converters if there has been some kind of trauma, such as extended engine misfires, fuel injectors stuck open for a period of time and so forth. You really need to test the vehicle and monitor component performance before guessing at sensors. www.repairpal.com/repair-shops