Brown's gas in Diesels

We are selling and installing a Brown's gas generator on large diesel trucks. Our unit works fantastic on Detroit 60 series with No O2 sensor as well as Cat twin Turbo pre 2005 no O2 sensor up to 30% however on Cummins ISX and Volvo we get zero results. Does anyone out there know why the Cummins and Volvo do not get better mileage from injecting hydrogen and oxygen when the other two get great results. I think it is in the ECM or the EGR system but do not have any details on the various systems. We know why it will not work on engines with O2 sensors therefore we will not install since we know there will be no gain. Since we are adding clean fuel there should be consistent results all things equal. Thanks In Advance.