If you are considering Oracle Trace, you must be able to get a single user to re-create the problem in a single Oracle session.
If so, you can trace just that session. This will require co-operation from both the user and the DBA, so make arrangements with them both privately, and then get them on a conference call. Get the user to open up their Oracle session, then give the DBA a moment to find the session ID. The DBA can then launch a trace directly on that session, generating a trace file. If the user can repeat the performance problem, then get them to close their session; this will close the trace. Now you have a trace file to run through TK*Prof.