WMI IIS Impersonation - Access is denied

Active Directory, Windows 8

If I logged on with user "xxx" and runs application with such code:

//WindowsIdentity.GetCurrent().Name - is "MyDomain\xxx";
var connectionOptions = new ConnectionOptions
{
  EnablePrivileges = true,
  Impersonation = ImpersonationLevel.Impersonate
};
var scope = new ManagementScope(
  string.Format("\\\\{0}\\root\\CIMV2", computerName),
  connectionOptions);
scope.Connect();

it works well.

However when runs this code in IIS on the same mashine I'v got exception:

// WindowsIdentity.GetCurrent().Name - is "NT AUTHORITY\SYSTEM" or "IIS APPPOOL\DefaultAppPool", tryed both
var windowsIdentity = User.Identity as WindowsIdentity;
if (windowsIdentity != null)
{
  using (windowsIdentity.Impersonate())
  {
    // WindowsIdentity.GetCurrent().Name - is "MyDomain\xxx";
    var connectionOptions = new ConnectionOptions
    {
      EnablePrivileges = true,
      Impersonation = ImpersonationLevel.Impersonate
    };
    var scope = new ManagementScope(
      string.Format("\\\\{0}\\root\\CIMV2", computerName),
      connectionOptions);
    scope.Connect(); 
    // throws exception "Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))"
    // my other code here        
  }
}

Used Windows Authentication:

<authentication mode="Windows" />
<identity impersonate="false" />

Tried run AppPool as ApplicationPoolIdentity and as System. Tried grant "Act as part of the operating system" for AppPool. The result is same, I always got "Access is denied".

Why I've got this exception? Should I do something else than just Impersonate or maybe grant some privileges for AppPool?