Sobs 1997 900 turbo having trouble with running

Saabs can be prone to floating ground issues in some of the light fixtures. My older one had this happen in particular, when the ground plane in the tail light cluster rusted and isolated the ground on a bunch of lights. It turned into a bypass where brakes, blinkers, emergency, all would make all the lights flash kind of dimly.

You should be able to remove the rear light clusters from inside the trunk. Look and see if there is corrosion, or signs that the ground plane - should look like a large scale printed circuit board, is damaged. Clean it off with a wire brush. if the ground plane is broken, you'll want to either get a replacement base plane, or, if you re-connect the ground, use some heavy wire to solder it back into connection so that it can handle the current for the lights.

I hope this might help!