Slow PowerShell execution of Microsoft Exchange 2013 commands from c#

Question

I have the following code that executes an exchange cmdlet. It works fast with command that return some output but work slow if command has no output.
for example
Invoke("Get-Mailbox")
prints following output:  
Begin execution at 11:44:43
Finish execution at 11:44:51
Output :
Administrator
Discovery Search Mailbox
Artem Romanchik
Execution time was about 8 second(6 second for loading exchange snappin + 2 seconds for command execution)
Slow example is
Invoke("Set-Mailbox -identity tema -MaxSendSize 10MB")
Begin execution at 11:53:34
Finish execution at 11:54:36
Output : 
Now it was 62 seconds(2 seconds for command and 60 seconds of waiting for something)
How can I reduce execution time of second example?
Invoke method code:
public void Invoke(string command)
var config = RunspaceConfiguration.Create();
PSSnapInException warning;
config.AddPSSnapIn("Microsoft.Exchange.Management.PowerShell.Snapin", out warning);
using(var runspace = RunspaceFactory.CreateRunspace(config))
runspace.Open();
using(var _psInstance = new RunspaceInvoke(runspace))
var psCommand = new PSCommand();
Console.WriteLine(String.Format("Begin execution at {0}", DateTime.Now.ToLongTimeString()));
var result = _psInstance.Invoke(command);
Console.WriteLine(String.Format("Finish execution at {0}", DateTime.Now.ToLongTimeString()));
var output = "";
foreach (var line in result)
if (line == null)
continue;
output += "\n" + line.BaseObject.ToString();
Console.WriteLine(String.Format("Output: {0}", output));
runspace.Close();

Answer 1

On 2010 and 2013 Powershell is throttled
http://technet.microsoft.com/en-us/library/dd298094(v=exchg.150).aspxyou might want to do some testing with a user that has throttling policy disabled. Also you might want to check the logs on the CAS server the request are going through eg \Microsoft\Exchange
Server\V15\Logging\CmdletInfra you should be able to determine from these if your being throttled.
Cheers
Glen