4WD is not an issue AFAIK, more a case of whether the ECU is correcting the commanded values to protect itself.
The commanded values within Nistune for an R34 GT-t/RS4/RS4S look identical but some tables are not visible within Nistune so it isn't always easy to know if the output from the ecu isn't altered.
Keep in mind Nistune is a work in progress.