Npc's and creatures which i create by duplicating a exsisting npc or creature by saving the creature or nps with a new ID reacts slower than the orginal creatures. When i run forwards them while they have a clear view it takes several seconds before they activate combatmode.

What's wrong? I've checked the ai tab where combat is set to 100

I'd verify to:
- have placed a new exact clone (that is, ALL stats are the same as the original ) near the original.
- the clone is placed in game from inside TESCS, not by script/console at gametime
- you are testing from a fresh new game
having verified the previous 3 points, if reaction speed differences stay, a possible explanation could be that the AI initializes/works with objects in creation order, so original objects have priority?