Gecko Breath ammo looks quite difficult to balance, because of it's damage type, obviously. We can again make it rare, unless someone has some other GOOD idea.
Okay folks, I have something to start with, featuring stats changes for flamer and gecko breath ammo and pyromaniac perks:
Actual pyromaniac perk is +20 flat damage each.
Flamer damage is 100-125=>112 average
(112-4[DT])*0.7[CA mk2]+40[2 perks]=115 damage
Pancor damage is 22-30=>26 average
(26*5-1*5[DT rounded up])*0.7=88 damage
Instead of adding 20 flat damage with each perk and nothing with pancor, we could:
-set +20dr mod on gecko breath
-add +5 flat damage instead of 20 (like fastshot) and -10 dr with each pyromaniac perk
-add 5 min and max damage to flamer
New flamer damage (both perks) is 105-130=>117 average
(117-4[DT])*0.9[CA mk2]+10[2 perks]=112 damage
New pancor damage (with both perks) is 22-30=>26 average
(26*5-1*5[DT rounded up])*0.70+10=98 damage
New pancor damage (with 1 perk)
(26*5-1*5[DT rounded up])*0.60+5=80 damage
New pancor damage (no perk)
(26*5-1*5[DT rounded up])*0.50=63 damage
After fix:
-flamer damage is almost the same with both perks (-3 average damage)
-pancor damage without perks was decreased from 88 to 63
-having one pyromaniac increases damage to 80 (still lower than actual)
-having both perks increases damage to 98 (better than how it is now, but at the cost of 2 perks, a specific build)
It might not be perfect but on the paper it seems to work, since having both pyromaniac perks will be at the cost of a third lifegiver or a even tougher, 285 hp and 65 dr with beer and psycho or 245 hp and 75 dr with same perks. And of course gecko breath shells should stay non craftable and expensive. Any knockdown effect should also be removed with that ammo. It burns you, but can't push you down like slugs. Same as frag/plasma grenades. Maybe increase a bit the knockdown effect on slugs to make it also a good choice if you don't have any perks. Something else that could be good, but I don't know if the engine allows that, is to lower pancor range from 25 to 20 when it's loaded with gecko breath.
A big set of changes for the balancing of a single weapon, but that's the best I could think of right now.