Hello Dell
That’s an overload that uses RAS to bridge to BOE. It will use the RAS server in the back-end and may not perform as well as the PageServer.
For a 3.1 to 4.0 migration, I'd highly recommend avoiding this type of call since the 4.0 runtime is only supported for fully managed scenarios and the reportdocument SDK is only supported in the 13.x runtime. Because of this, the .Load overload and any BOE dependencies were removed from the 13.x runtime.
Since the app already has an infoobject, most of the work is done. If the app sets params/logons to the reportdocument object, change the project to use CD.Enterprise.Desktop.Report object(cast the infoobject to a Report object and use PSReportFactory for the reportsource) or ReportClientDocument object (create ReportAppFactory from enterprisesession and create reportclientdocument from reportappfactory.Opendocument (infoobject.ID)).
But than, I suspect the last paragraph was obvious. E.g.; I am pretty sure you know more about this than I do 
. E.g.; love to read your posts. I've learned more from them than from most any training I've done here.
- Ludek