Re: reverse polarity
How well does it run when not at idle ? I would suggest taking it to someone who has an code scanner and knows how to use it.
For your sake I hope it is electrical but if that was oil on the exhaust tips in the video it is probably mechanical. If so I would at least have a compression test done and preferably a leakdown test if you can find someone who knows how.
If it only misfires at idle and has good power we can talk about other options.