Наилучшей скорости можно достичь, собрав все данные в массив и записав все это на лист за один раз.
В вашем коде также есть масса других проблем, см. Примечания нижеотмечены <~~~
Sub FindResults()
'Selecting file for import
Dim FileSelect As FileDialog '<~~~ use explicit type
Dim PlateMapFolder As String
'<~~~ declare all Variables
Dim SelectedFile As String
Dim strFileContent As String
Dim strResults() As String
Dim arrResultsLine() As String
Dim arrResultsTab() As String
Dim i As Long
PlateMapFolder = "C:\"
Set FileSelect = Application.FileDialog(msoFileDialogFilePicker)
With FileSelect
.InitialFileName = PlateMapFolder
.AllowMultiSelect = False
.Title = "Please select associated run"
.Show
If .SelectedItems.Count = 0 Then
Exit Sub
End If
'SelectedFile = Dir(.SelectedItems(1)) '<~~~ No need for Dir here
SelectedFile = .SelectedItems(1)
End With
Application.ScreenUpdating = False
Application.DisplayAlerts = False
'Splitting SelectedFile
Const strSearch = "[Results]"
Dim intFileNumber As Integer
intFileNumber = FreeFile
Open SelectedFile For Input As intFileNumber
strFileContent = Input(LOF(intFileNumber), intFileNumber)
Close intFileNumber '<~~~ close file after use
'Split result file at [Results]
strResults = Split(strFileContent, strSearch)
'Split line breaks
arrResultsLine = Split(strResults(1), vbLf)
'Split each line by tab
' <~~~ declare and size array to hold results
Dim Res As Variant
ReDim Res(1 To UBound(arrResultsLine) - 2, 1 To 5)
'intRow = 1 <~~~ not needed
'<~~~ this will skip first and last line after [Results].
' Is this what you want?
' If not, also adjust Redim size
For i = 2 To UBound(arrResultsLine) - 1
arrResultsTab = Split(arrResultsLine(i), vbTab)
'<~~~ collect data into array
Res(i - 1, 1) = arrResultsTab(0)
Res(i - 1, 2) = arrResultsTab(1)
Res(i - 1, 3) = arrResultsTab(2)
Res(i - 1, 4) = arrResultsTab(3)
Res(i - 1, 5) = arrResultsTab(4)
Next i
'<~~~ write to sheet in one go
Sheets("RawData").Range("A1").Resize(UBound(Res, 1), UBound(Res, 2)).Value = Res
'<~~~ turn these back on!
Application.ScreenUpdating = True
Application.DisplayAlerts = True
End Sub