I think 2003 saab 9-3 are the second generation models and BlueSaab does not work with it.
I guess there was some other way to connect aux or bluetooth streaming to these models, which did not require this much of modification and DIY spirit :D
I have a 2006 9-3ss (old sound system) and bought this device: https://saabplus.com/ (I'm not affiliated, only a customer)
The one I received was actually a model "2" which has a microphone input so it can be used as a handsfree for your phone as well.
If you already have aux, this device replaces it. If you don't have aux, this will need to be enabled with a TECH2.
This is however not nearly as solid a product as BlueSAAB. it cuts off the connection when moving the key to OFF since it's powered by the 12v power outlet (cigarette lighter plug). Also wires for power are just loosely pushed in place on some connectors behind the dash, so it seems pretty fragile. I haven't had any problems though. I guess I could tab into a wire with 12v that switches off when the radio is powered off, but I haven't had time to look into it yet.