Web Api 2 OWIN Selfhost handle multiple concurrent requests

I have a selfhosted web api using OWIN, and I seems to struggle on concurrent connections. When I run a stress test with 50 concurrent get events, the response time is increasing A LOT, even tho the operation is quite simple, return 200 OK with the id typed in the uri.

How do I my web api OWIN and api controllers to run simultanious per requests??

Here's a sample of my project:

Startup class

public class Startup
{
    public void Configuration(IAppBuilder appBuilder)
    {
        try
        {
            appBuilder.UseWelcomePage("/welcome.html");
            appBuilder.UseErrorPage(new ErrorPageOptions
            {
                ShowExceptionDetails =
    #if DEBUG
                true
    #else
                false
    #endif
            });

            Debug.WriteLine($"Setting Web Api Configuration up...");
            var apiConfig = ConfigureWebApi();
            appBuilder.UseWebApi(new HttpServer(apiConfig));
            appBuilder.UseCors(CorsOptions.AllowAll);

            Debug.WriteLine($"Completed Web Api configuration.");
        }
        catch (Exception ex)
        {
            Debug.WriteLine($"Failed to complete Web Api setup.", ex);
            throw;
        }
    }
}

Controller

public class TestController : ApiController
{
    public async Task<IHttpActionResult> Get(int id)
    {
        return Task<IHttpActionResult>.Factory.StartNew(() => {
            try
            {
                return Ok(id);
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.Message, nameof(Get));
                return InternalServerError();
            }
        });
    }
}

My console startup of web api:

public static void Open()
{
    _webApp = WebApp.Start<Startup>(HostAddress);
    Console.WriteLine($"Host open -> {HostAddress}");
}