Why don't you use a stand alone ECU that will control the ignition and fuel? (Keep the OEM ECU for the rest). Install load resistors to foul the OEM ECU.
Start with base maps, then spend a day on the dyno to tune and you should be good to go.
You may loose DSC, but if you drive a twin turbo V8, you shouldn't need DSC anyways.

Are you going to lower the CR with the new pistons?

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