Before you install add-on mods, you'll need to install gameconfig

https://www.gta5-mods.com/misc/gta-5-gameconfig-300-cars

and you'll need this two

Packfile Limit Adjuster

https://www.gta5-mods.com/tools/packfile-limit-adjuster

Heap Adjuster

https://www.gta5-mods.com/tools/heapadjuster
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This mods needs ELS(Emergency Lighting System) let emergency light work

https://www.lcpdfr.com/downloads/gta5mods/scripts/13865-emergency-lighting-system/
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Recommend use this two siren mods

Taiwanese siren | ORCHID（蘭記）PA560S
https://www.lcpdfr.com/downloads/gta5mods/audio/38072-taiwanese-siren-orchid%EF%BC%88%E8%98%AD%E8%A8%98%EF%BC%89pa560s/