Search performance sluggish with DataTable with 30,000 rows

There are two functions attached.
Function StartProcessingWithOptions(ByRef WL As Data.DataTable, ByRef GF As Data.DataTable, ByVal lnRate As Integer, ByVal FromSecondName As Boolean, ByVal UseMetaPhone As Boolean)
Dim Results As New Data.DataTable
Dim ResR As Data.DataRow
Dim WLR As Data.DataRow
Dim GFR As Data.DataRow
'Dim lcNames As String
Dim i = 0, p As Double
Dim lcPerson As String, S1 As String, S2 As String, lcCurrentName As String
Results.Columns.Add(New Data.DataColumn("Person", System.Type.GetType("System.String")))
Results.Columns.Add(New Data.DataColumn("Group", System.Type.GetType("System.String")))
Results.Columns.Add(New Data.DataColumn("CustomerName", System.Type.GetType("System.String")))
Results.Columns.Add(New Data.DataColumn("CustomerNumber", System.Type.GetType("System.String")))
...