If you experience long request times in your web application without a high server load you should check processing of Microsoft Dynamics CRM requests. These are processed serially.
Since the CRM SDK has some strange logic, which does not handle parallelism very well, i needed a proper solution for connection pooling.
Here is my connection pooling mechanism for ASP.NET MVC 5.
Setup you connection string in the .env file.
Have a look in the Global.asax.cs for the configuration.
Just run the application.