Driver Prioritization sets Priority level for business strategy and project impacts.
Here below is the given code to create Driver Prioritization using PSI.
First I am exporting Driver Prioritization data from one environment and then importing data into another environment.

Exporting: Use export environment credentials

DriverWebSvc.DriverPrioritizationDataSet driverPrioritizationDataSet = new DriverWebSvc.DriverPrioritizationDataSet();

// Reads the list of prioritizations
DriverWebSvc.DriverPrioritizationDataSet prioritizationList = driverWebSvc.ReadPrioritizationList();


foreach (DriverWebSvc.DriverPrioritizationDataSet.PrioritizationRow prioritizationRow in prioritizationList.Prioritization.Rows)
{
	DriverWebSvc.DriverPrioritizationDataSet driverPrioritizationDataSetTemp = driverWebSvc.ReadPrioritization(prioritizationRow.PRIORITIZATION_UID);

	// Merging Prioritization data table
	driverPrioritizationDataSet.Prioritization.Merge(driverPrioritizationDataSetTemp.Prioritization);

	// Merging PrioritizationEntries data table
	driverPrioritizationDataSet.PrioritizationEntries.Merge(driverPrioritizationDataSetTemp.PrioritizationEntries);

	// Merging DriverRelations data table
	driverPrioritizationDataSet.DriverRelations.Merge(driverPrioritizationDataSetTemp.DriverRelations);
}

Importing: Use import environment credentials

DriverWebSvc.DriverPrioritizationDataSet targetDriverPrioritizationDataSet = driverWebSvc.ReadPrioritizationList();

List<Guid> prioritizationUids = new List<Guid>();
foreach (DriverPrioritizationDataSet.PrioritizationRow prioritizationRow in targetDriverPrioritizationDataSet.Prioritization.Rows)
{
	prioritizationUids.Add(prioritizationRow.PRIORITIZATION_UID);
}

if (prioritizationUids.Count > 0)
	driverWebSvc.DeletePrioritizations(prioritizationUids.ToArray());

foreach (DriverPrioritizationDataSet.PrioritizationRow prioritizationRow in driverPrioritizationDataSet.Prioritization.Rows)
{
	try
	{
		DriverWebSvc.DriverPrioritizationDataSet drvDS = new DriverWebSvc.DriverPrioritizationDataSet();

		// Adding Prioritization row
		drvDS.Prioritization.Rows.Add(prioritizationRow.ItemArray);

		// Adding Prioritization Entries row
		foreach (DriverPrioritizationDataSet.PrioritizationEntriesRow prioritizationEntriesRow in driverPrioritizationDataSet.PrioritizationEntries.Rows)
		{
			if (prioritizationEntriesRow.PRIORITIZATION_UID == prioritizationRow.PRIORITIZATION_UID)
			{
				drvDS.PrioritizationEntries.Rows.Add(prioritizationEntriesRow.ItemArray);
			}
		}

		// Adding Driver Relations row
		foreach (DriverPrioritizationDataSet.DriverRelationsRow driverRelationsRow in driverPrioritizationDataSet.DriverRelations.Rows)
		{
			if (driverRelationsRow.PRIORITIZATION_UID == prioritizationRow.PRIORITIZATION_UID)
			{
				drvDS.DriverRelations.Rows.Add(driverRelationsRow.ItemArray);
			}
		}

		driverWebSvc.CreatePrioritization((DriverWebSvc.DriverPrioritizationDataSet)drvDS);
	
	}
	catch (SoapException sEx)
	{
		//log exception
	}
	catch (Exception ex)
	{
		//log exception
	}
	
}

Hope this code will help you.Thanks