I found this for Varnish:
http://www.vbulletin.com/forum/forum...in-share-yours
From 2011, but still might be helpful.
What about your server though? What kind of VPS / Dedicated server is it? What is your RAM / swap? CPU, cores? What kind of nginx configuration(s) are you running for nginx? And what is your main nginx configuration file? Eg, your worker_processes and worker_connections settings. And with FPM, are you using static, dynamic or on demand?
And are you using gzip?
There are so many variables with nginx/fpm that can make a huge difference on how fast your vBulletin setup will run.