Ive been using glimpse to try to address some slow page issues, only to discover that glimpse is the cause. The page requests are 30000+ seconds, without glimpse they are instan
Go to /Glimpse.axd
and uncheck all the Glimpse addons/tabs. It will give you the XML config needed to copy & paste into your web.config. In my case, it was Routes, probably due to extensive use of attribute routing. Others have mentioned Cache and Metadata, so start by ignoring all, then comment out a few at a time until you find what slows down Glimpse.
Note that the below config may not work for you, if you have different addons or versions installed.