Can catalytic converter cause this?

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Camry running rough. Have to floor gas pedal to get gas and start moving. Check engine light has been on for a while. I thought it was water in gas, freezing, as it has been very cold. Put 2 bottles of dry gas in, no help. when engine is missing and sputtering, the check engine light blinks. I thought it could also be bad gasoline. Check engine light code is 420(cat)