I have a fiesta st180 (mk7) and recently I got the revo stage 1 software installed

immediately I went to show my Friends and the one who was in the back seat noticed small backfires on gear shifts 

Which got me thinking what mod will make it backfire more/louder?

also I don’t want to get a crackle ECU map for several reasons

mainly because I want it to backfire naturally instead of faking it

Doesn't sound like it's actual backfire, just that the map is programmed to make some pops.

And you can't make it naturally, the map adjusts the valve timing to allow unburnt fuel to exit through the exhaust and it ignites on the way out in the hot exhaust causing the pops.

It used to happen "naturally" just due to the lower efficieny of older engines, the timing is so precise on modern engines, tuned for best performance/efficiency it would never happen, but they intentionally "make it worse" to cause some pops.

Ford did this themselves on the mk3 RS and they've also done it on fast Fords since, in sport/track modes.

I see. 
so there is no real way of doing it other than forcing it with a crackle map?

maybe a res delete or an induction kit might make a difference?

 

Decat is the best way to be able to hear the bangs once you get them.

Its all in the mapping though. You're best getting a custom remap then the tuner can do it how you want. They can make it so you get a bang on gear change or full overrun if you want to go OTT.