While creating a REST component to execute some operations against an exchange instance, I noticed some performance issue. Surprisingly the unit/integration-test suite was a lot faster when Fiddler was active.
This seems to be some kind of default problem when developing .NET application as Telerik even added its own page for this scenario.
However, if none of those apply to your situation – as it was the case for me – you should read on to get an idea on how you can debug this further (and you even might have the same problem!).