I had a very slow power pivot report and wanted to identify which query was taking the time so I enabled the tracing
The trace is generated by default in your desktop, the trace is a SQL Profiler trace so you will need to use SQL Profiler to open it.
When is open, organize the columns by eventclass
Now filter the eventSubclass to 25 which is execute SQL
Now you can focus in Progress Report End event and check what TSQL is taking longer