You cannot specify that a file is Tab-delimited in the connection string. You can only specify that it is delimited. You specify that the delimiters are Tabs elsewhere, either in the Registry or a schema.ini file. Note that the first example here specifically mentions the Registry. You can find reference to a schema.ini file here.

As an alternative, you could use a TextFieldParser and load the data into a DataTable yourself, which would allow you to avoid specifying the delimiter in a secondary location.