optimum gear change and backfire

always wondered this and asked in a lobby the other night but no one really had a definitive answer.

when you change gear and get a flame from the exhaust is this to indicate you`ve changed at the optimum point?

when i was testing one of my porsches i found what seemed to be the sweet spot for changing gear and always had this spit of flame so just make me wonder

Really only works for me that have race exhaust and engine upgrades such as camshaft, displacement and ignition, as well as some sort of aspiration.
Its never really shown on cars without all this iv noticed.