9.1B is, of course, ancient, obsolete and unsupported. You really ought to upgrade. There is no technical reason that you cannot get to 9.1E04. If you can compile code there is nothing stopping you from upgrading all the way to 10.2B.
There are almost always ways to make things better. Even with 9.1B.
From a performance perspective Syteline is a "target rich" environment.
Re-indexing rarely helps.
Dumping and loading may help but to really get bang for your buck on that front you need to implement properly designed storage areas. Doing that properly can have an enormous impact.
There are also, of course, some things you might be able to do with startup parameters. In particular those related to caching either at the db or the session level such as -B & -mmax.
If you have an enterprise license you should be using -spin.
You might also want to consider bringing in a consultant.