How to debug JSF page rendering

It looks like my J2EE application is loading slower than expected. We checked DB side and it looks like UI is slower than expected. Is there any way to throubleshoot and find out the cause?

This application is AJAX based and most of the AJAX calls are triggered by calling js function and then servlet call using Prototype or Rico livegrid library functions. JSF version is 2.2.4 now and it was 1.2 earlier. That's why we are using old model AJAX instead of JSF2 AJAX. Only few pages using JSF2 AJAX. Most of the calls will be JS function > Servlet > EJB.