Working on a similar problem as OP, so i hope people don't mind the bump.
Adding an item to the Suburbs distribution just like OP, although not a lighter, and it is causing tremendous lag for whatever reason. I even moved the weighted number around to no avail. Then I loaded another mod that modified the same table and no lag.
I am adding a lootable token type item, and an exchange system to go with it.
>Media
>>Scripts
>>>Module Necrophilia (I can include details other, but my guess is that this is the problem)
>>lua>server>Items>Dustloot.lua
require 'Items/SuburbsDistributions'
table.insert(SuburbsDistributions["all"]["inventorymale"].items, "Necrophilia.BlueDust");
table.insert(SuburbsDistributions["all"]["inventorymale"].items, 200);
table.insert(SuburbsDistributions["all"]["inventoryfemale"].items, "Necrophilia.BlueDust");
table.insert(SuburbsDistributions["all"]["inventoryfemale"].items, 200);
Anyway, I just figured out writing this that the module name is probably the problem. So I need to load it into the game properly somewhere else?