Handling large pac files in C# HTTPWebRequest

Question

I currently have a C# application which makes frequent web requests that have to potentially go through proxy authentication. In this situation, a large PAC file (200kb+) is used to automatically configure the proxy and is stored on a remote server.

When initializing the HttpWebRequest I have been setting the default proxy by using 'WebRequest.DefaultWebProxy = WebRequest.GetSystemWebProxy()' in the constructor of my connection class and then reusing the WebRequest.DefaultWebProxy throughout the rest of my connection class.

Unfortunately this setup is extremely slow! I was wondering if a more efficient way of doing this exists.