2003 SAAB 9-3 repair Question acceleration problems

First of all, DON'T "over" rev the engine. The first thing I would check in this situation is the throttle body. Take the duct off going to it and open the throttle blade. If it has never been cleaned, it will be black with gunk. This closes off airflow at start up and at idle (the reason you have to rev it to keep it running). You will need to get some throttle body spray cleaner (not carb cleaner), some rags and an old toothbrush. Put a rag under the throttle body to catch any spilled cleaner. If it is a turbo, you don't have to worry about this, since the throttle body is vertically mounted. Soak a rag in cleaner, hold the throttle blade open, and wipe out as much gunk as possible (you may want to wear solvent resistant nitrile gloves to protect your hands), then spray the inside of the throttle body. Use the toothbrush to get all of the gunk out. Temporarily reinstall all intake ducting and start the engine occasionally to clear any liquid cleaner from inside, because you could hydro-lock the engine if liquid goes into the cylinders. You may have more problems, but you must always start troubleshooting with a clean throttle body. To prevent this, it should be cleaned every 30k miles.