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

 

Most of the time if the misfire occurs on WOT then you have a clogged injector.
Put a bottle of Seafoam into the tank and pray for the best.

 

Or Techron Fuel System Cleaner in the gas as I found it more effective than Sea Foam. Or both. Check your engine air filter too.

Hope you do not have a failing spark plug coil on cylinder 3, or a bad 02 sensor. If #3 is on the rear bank which is hard to access, then all 3 coils and plugs should be replaced as you are already passed the recommended maintenance interval of 120,000 miles. Although many go farther before changing spark plugs, if there is an issue back there it is time to replace all 3 plugs & coils in the rear.

In the front bank you can get away with just the plugs as they are easy to access later if you need a coil next year.

I doubt it is the converter and they cost a fortune.

 

I'm sorry what is wot and I put sea foam in it and nothing changed if I floor it then it misfires and I have to reset then it's fine no rough idle or anything

 

wot - wide open throttle. Basically flooring it