In situations where performance is being degraded by a single or specific W3WP.EXE processes and you need to isolate a process for further troubleshooting you can do the following steps.
From IIS Manager, select and highlight the server name.
After opening the Worker Processes tool, you should see the following. Notice the the friendly description of resource usage.
You can also run the following command from a command prompt that give you a PID that you can reference with Task Manager.
C:\Windows\System32\inetsrv\appcmd.exe list wp
For information on gathering Worker Process information in Powershell: Query the active worker process information in IIS 7.X using Powershell – WebTopics