Coilpack loom? Coilpack loom is just wiring, it will either work or it wont. Are you sure all of your coilpacks are actually firing. When the car is running, unplug each coilpack one by one and if the cars idle drops a bit then that cylinder is firing. It the revs stay exactly the same then somethings wrong and that cylinder isnt firing. Swap that coilpack with another cylinder and if it still doesnt fire in the same one then the coilpacks are fine but something else is still wrong. Just work through everything untill you find the problem. Igniter, Sparkplugs, AAC valve, AFM. Lots of things that it could be.