I found out when an android (from android tiers) mod (a t1 android, but that might not be relevant) is equiped with a machine pistol, without ammo (yayo combat 3 adds ammo), and you draft that android, the fps drops to like 1. Using performance analyzer I found out these 3 lines spiking to 400ms:

Void Postfix(Verse.Pawn) yayoCombat.patch_Pawn_TickRare

Void Postfix(Boolean ByRef, Verse.Pawn, Verse.LocalTargetInfo) TerrainMovement.ReservationManager_Reservation_CanReserve_ReachCheckPatch

Void Postfix(Boolean ByRef, Verse.Region ByRef, Verse.TraverseParms, Boolean) TerrainMovement.TraverseParms_Allow_Movement_Restrictions

I tested picking the unloaded machine pistol with other, normal human pawns, and there was no lag spike, so it must be a problem with Yayo+AndroidTiers compatibility (I am out of ammo so I cannot test if the weapon being out of ammo also makes a difference). I don't know if it is something that has to be fixed on Yayo mod or AndroidTiers mod, but I left this on yayo's mod page and here in case anyone wants to take a look.