Engine light codes PO491 and492.

[Jinx]

I got a check engine light this morning
Had Advanced Auto pull the codes.

Codes are PO 491 and 492.

Can anyone give me a idea what would cause
These. And what items do I check or replace
To fit the problem.

Is there anyway to reset the computer?
No change in operation. No misses
Or backfires still runs smooth.

Searched did not find any info.

Thanks in advance for the help

Bill and Jinx