im_foken_stup These aren't mods. The red insta kill and extra health are perma perks which only work on Tranzit, Die Rise, and Buried. They are a intended feature of the game. They way you obtain the red insta kill is by not killing any zombies during 1-2 insta kills. The way to lose red insta kill is getting hit by a zombie during insta kill. The way you obtain extra is health is by bleeding out 3 times before round 15. The way you lose the extra health is by reaching round 15, then the next time you down you'll have normal health.