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@asdw1154 if you're only using this mod, use OpenIV to copy the base game common.rpf into your mods folder. then go to \mods\common.rpf\data\ and edit relationship.dat to whatever you want, which gangs hate eachother etc. For example: Ballas and Families hate eachother (AMBIENT_GANG_BALLAS and AMBIENT_GANG_FAMILIES). I dont think you can 'join' a gang, but you can set them to RESPECT PLAYER and they wont attack you when you shoot something else, they will attack any 'bodyguard' or 'follower' spawned with a script if you shoot though, even if they are the same gang ped.

Then use OpenIV to edit this mod's \mods\update\update.rpf\common\data\levels\gta5 and edit pop_cycle.dat. Here you will want to change for example the CHAMBERLANE and DAVIS areas. The first row is midnight and then every row is +2 hours after that. So you will want to edit the first and last rows so that "Chamberlane_Gang" and "Davis_Gang" population groups mingle (use edit mode to type or copy paste the ped group's name). For this to work, the numbers need to add up to 100. So for example in CHAMBERLANE i change the ped part in the line to this:
"peds Chamberlain_SC 40 Chamberlain_Tramps 10 Chamberlain_Gang 30 Davis_Gang 20 Birds_City 00"
- Instead of a 'full' 40% of peds spawned being Families, now it's 30% with 10% chance of Ballas appearing at this time.

Now the gangs will enter eachother's territory around 10pm-12pm (which i guess is when street thugs are mostly 'active') in the Grove street and Chamberlane area and get into figths dynamically - i have seen them randomly run up and stab a lone guy. Random 'drive-bys' where they shoot from a car, or shoot at an enemy car. This is all already coded into the base game behaviour, it just isn't 'activated'. And during the day it is quiet, but if you hang around the border of Grove street near Chamberlane, sometimes it can just happen that the two groups mingle naturally anyway and a fight will happen. but this is rare, so the Pop_Cycle edits is needed.

Bonus: if you edit the percCopChance in pop_cycle.dat you can re-enable cops ambiently spawning in the world. This makes the game much harder with this mod (and reminds me of my days on real roleplay servers with power-trip cops pulling me over all the time🤣)

This way you can totally customise who spawns where, what time during the day, how many of each group/type and all of that. Play around with it or maybe use AI to edit it for you, i haven't tried that.