I’ll avoid questioning the reason for your post, but the quickest reply would be to use the BO trace feature.
In all fairness you can only answer that question by starting with some questions of your own to narrow it down, so if BO trace is not what they’re looking for then:
Which product and version i.e desktop, zabo or webi / v5 - v6 - XI ?
By slow - is this based on results returned or query runtimes?
i.e. Results returned would probably be a memory issue.
The universe design can be ignored - assuming the same generated sql is used so the order of tables in the where clause etc should be the same.
Zabo and webi will be queuing for connections as well as being impacted by server loads and activity, admin settings, network bandwidth, caching etc.
The universe connection should be examined in all instances and you need to ask the DBA id the BO connection id has been restricted in any way.