Bob, do you have a cache installed? That's what it generates a SQL spike...
I actually opened a ticket for this matter to vBulletin, their own code generates the same results...
http://www.vbulletin.com/forum/bugs3...iew&bugid=2481
So far Scott and Freddie are looking for a solution, the bug was confirmed.
The issue we are dealing with is the following:
Once a query is cached, the SQL execution time (%) gets low, only the connection time and other non cached SQL processes are filtered by vBMicroStats. Then, once the queries are not in the cache anymore, BOOM, a heavy SQL demand is passed to the server.
That explains the high SQL % you get sometimes. I'm in the same boat, no fix possible in my eyes, that's the way caches work.
I hope vB Team will find a trick in their hat. read more in the bug thread I opened.