Advance Components
WARNING: This page is about a different car, the 2001 Saab 9-5 and 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
Timing advance is controlled by the ECM. Trionic engine management system uses spark plugs to measure combustion chamber resistance, which is in turn used to control ignition timing, turbo charge and throttle position.