Dclackjr03

Runs and drives fine for a 3 days unless I floor.it then check engine light comes on and vsc which I know only is on due to check engine light but codes have been read twice the first time was misfire on cylinder. 3 and you could tell it was misfiring I reset the battery and lights go off and the misfire goes away the second time I got codes read misfire cylinder. 3, bad converter, and bad downstream 02 sensor it's got me lost on what it could be car has approx. 139000 miles any help would be greatly appreciated