exhaust backfire

getting back to induction cross-fire;
>If a cylinder fires another still on the power-stroke, that's no big deal.
>But if it fires one on the exhaust stroke, with headers that's no big deal, unless there is enough unburned fuel still in that exhaust, and enough oxygen to support further combustion. A leaky header flange would be the hot ticket for the introduction of fresh air to support that, which is why, oh so long ago, I inquired about "induction cross-fire.
>But if a cylinder fires another still on the intake stroke ................. that can't be good,lol.