I wouldn't. They are quick enough standard. If you do loads of miles, then I would strongly advise you didn't, as Saab's are thirsty enough, and any performance you do would turn it into a guzzler.
Mind, if your not interested in that (and I know its a bit like the pot calling the kettle black me preaching about fuel eco!) then a remap on the new Saabs should get you some extra power. What turbo do you have on it? if it is a large turbo with a low setting, maybe getting a evc to alter the boost would make a large difference. Just make sure your cooling system can take it.