Is there any way to run a secondary fuel system triggered by boost. I know MSD makes a nice boost timing retard system that can take care of timing issues. I am not sure how it would work but plumbing a couple of in-line injectors into the intake tract that would come on as it sensed boost conditions. As boost came up the injector duty cycle could be increased. I am not personally familer with how the Caddy's BCM/PCM works. As my car is a standard trans and does not use anything but the main Caddy ECM.