Coils? Plural? What sort of coil, oil can or transformer? Is this a distributorless ignition?

Can you see 12-16V square waves going into the low voltage side from the ECU? If so, have you checked for carbon tracking down the outside of each spark plug? Did you do Mark's spark plug test in the dark to check if the HT is shorting along the outside of the plug leads? Are the plug leads clean and free of oil?

Coils do fail, but for two to fail at once is odd. It would be helpful if you could decribe the ignition system a bit more.