Exportação RDLC LocalReport para Excel muito lenta

using Microsoft.Reporting.WebForms;
using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Linq;
using System.Text;

//As you would expect, the new assembly WebReportviewer.FullTrustReportviewer
//all it does is just run the report. that's it. here is the code, it should be in a separated project:

namespace WebReportviewer
{
    [Serializable]
    public class FullTrustReportviewer : MarshalByRefObject
    {
        private ReportViewer FullTrust;
        public FullTrustReportviewer()
        {
            FullTrust = new ReportViewer();
            FullTrust.ShowExportControls = false;
            FullTrust.ShowPrintButton = true;
            FullTrust.ShowZoomControl = true;
            FullTrust.SizeToReportContent = false;
            FullTrust.ShowReportBody = true;
            FullTrust.ShowDocumentMapButton = false;
            FullTrust.ShowFindControls = true;
            //FullTrust.LocalReport.SubreportProcessing += LocalReport_SubreportProcessing;
            //FullTrust.LocalReport.SetBasePermissionsForSandboxAppDomain(new PermissionSet(PermissionState.Unrestricted));
        }

        public void Initialize(string DisplayName, string ReportPath, bool Visible, ReportParameter[] reportParam, string reportRenderFormat, string deviceInfo, string repMainContent, List<string[]> repSubContent)
        {
            FullTrust.LocalReport.DisplayName = DisplayName;
            FullTrust.LocalReport.ReportPath = ReportPath;
            //FullTrust.Visible = Visible;
            //FullTrust.LocalReport.LoadReportDefinition(new StringReader(repMainContent));
            FullTrust.LocalReport.SetParameters(reportParam);

            repSubContent.ForEach(x =>
            {
                FullTrust.LocalReport.LoadSubreportDefinition(x[0], new StringReader(x[1]));
            });
            FullTrust.LocalReport.DataSources.Clear();
        }

        public byte[] Render(string reportRenderFormat, string deviceInfo)
        {
            return FullTrust.LocalReport.Render(reportRenderFormat, deviceInfo);
        }
        public void AddDataSources(string p, DataTable datatable)
        {
            FullTrust.LocalReport.DataSources.Add(new ReportDataSource(p, datatable));
        }

        public SubreportProcessingEventHandler SubreportProcessing { get; set; }

        public static void LocalReport_SubreportProcessing(object sender, SubreportProcessingEventArgs e)
        {
            LocalReport lr = (LocalReport)sender;

            e.DataSources.Clear();
            ReportDataSource rds;

            if (e.ReportPath.Contains("DataTable2"))
            {
                DataTable dt = (DataTable)lr.DataSources["DataTable2"].Value;
                DataView dv = new DataView(dt);
                dv.RowFilter = string.Format("Id={0}", e.Parameters["Id"].Values[0]);
                rds = new ReportDataSource("DataTable2", dv.ToTable());
                e.DataSources.Add(rds);
            }
        }
    }
}

 public static byte[] GeneratePBAReport()
        {


            string l_spName = string.Empty;
            string l_reportPath = string.Empty;
            var repCol = new List<ReportDataSource>();

            var repParCol = new ReportParameter[1];
            if (id == "")
            {

                l_reportPath = HttpContext.Current.Server.MapPath("~\\.rdlc");
                l_spName = "";
            }
            else
            {
                l_reportPath = HttpContext.Current.Server.MapPath("~\\.rdlc");
                l_spName = "";
            }

            repParCol[0] = new ReportParameter("pID", "");

            var ds = new DataSet();
            using (var sqlCmd = new SqlCommand(l_spName, new SqlConnection(ConfigurationManager.ConnectionStrings[""].ConnectionString)))
            {
                sqlCmd.CommandType = CommandType.StoredProcedure;
                var sqlParam = new SqlParameter() { Value = "", ParameterName = "" };
                sqlCmd.Parameters.Add(sqlParam);
                sqlCmd.CommandTimeout = 300;
                using (var sqlAdapter = new SqlDataAdapter(sqlCmd))
                {
                    sqlAdapter.Fill(ds);
                }
            }

            var rds = new ReportDataSource();
            rds.Name = "";
            rds.Value = ds.Tables[0];
            //l_report.DataSources.Add(rds);
            repCol.Add(rds);

            rds = new ReportDataSource();
            rds.Name = "";
            rds.Value = ds.Tables[1];
            //l_report.DataSources.Add(rds);
            repCol.Add(rds);

            rds = new ReportDataSource();
            rds.Name = "";
            rds.Value = ds.Tables[2];
            //l_report.DataSources.Add(rds);
            repCol.Add(rds);

            rds = new ReportDataSource();
            rds.Name = "";
            rds.Value = ds.Tables[3];
            //l_report.DataSources.Add(rds);
            repCol.Add(rds);

            Warning[] warnings;
            string[] streamids;
            string mimeType;
            string encoding;
            string extension;
            string deviceInfo;


            deviceInfo = "<DeviceInfo><SimplePageHeaders>True</SimplePageHeaders></DeviceInfo>";

            return NewDomainReport.Render("PDF", deviceInfo, "-" , l_reportPath, true, repCol, string.Empty, new List<string[]>(), repParCol);
        }