You can try using fiddler and see the result. Also I would suggest you to once review your code and see if you are following certain optimizing standards like
Are you doing caching? It will really help you boost the performance.
Also make sure you are not iterating a lot many times. In-case you are fetching data from a sharepoint list in your webpart then make sure you are fetching only the fields that you require and not all the fields. Use SPQuery or SPSiteDataQuery object wherever required to filter down.
Also check for memory leaks using SPDisposeCheck.
Also there is a differnce when it comes to using list.Items.Count and list.ItemCount.
Apart from using Fiddler, just do your code review once for all these points and you will observe a performance increase.
Hope it helps.