ayuda con HttpWebResponse

Dim request As HttpWebRequest = CType(WebRequest.Create(pUrl), HttpWebRequest)
        request.Method = pMethod
        request.Accept = pAccept
        request.Referer = pReferer
        request.ContentType = "multipart/form-data: boundary=7d23e2a11301c4"
        request.ContentLength = secuencia.Length
        request.Headers.Add("Accept-Language", "es-cl")
        request.Headers.Add("Accept-Encoding", "gzip, deflate")
        request.Headers.Add("Cache-Control", "no-cache")
        request.Headers.Add("Cookie", String.Format(pToken, _TOUKEN_))  'aquí va el token entregado por el SII

        request.UserAgent = "Mozilla/4.0 (compatible; PROG 1.0; Windows NT 5.0; YComp 5.0.2.4)"
        request.KeepAlive = True

     
        ' Recupere el streamwriter para escribir la secuencia
        Try
            Dim sw As StreamWriter = New StreamWriter(request.GetRequestStream(), Encoding.GetEncoding("ISO-8859-1"))
            sw.Write(secuencia.ToString())
        Catch ex As Exception
            MsgBox("Error en metodo o forma de Envio")
        End Try

        Dim respuestaSii As String = String.Empty

        '
        '//// Recupere la respuesta del sii
        Dim response As HttpWebResponse = CType(request.GetResponse(), HttpWebResponse)
        Dim sr As StreamReader = New StreamReader(response.GetResponseStream())
        respuestaSii = sr.ReadToEnd().Trim()
        MsgBox(respuestaSii)