Most of the liter Gm V6 engines have a 6 coil towers. the firing order is usullay marked on the coils. You should see 1-4 on the first 2 coil towers, 3-6 on the second and 2-5 on the last. Put on the wires in this order. As for the Cylinders themselves, the fire wall or rear bank goes 1-3-5 from the pass ->driver side and the front goes from 2-4-6 from the pass -> driver side.