So i try to start the stang today and it turns over fine and then immediatly just drops to really low rpms and cuts off. If i give it gas it will stay on but the second i take my foot off the pedal it just stalls out. I managed to get it outta the driveway and down the road for like a half mile and then i pulled over and it ran fine... i went to advanced auto parts and had them test my alternator and they said it was bad so i got a new one and just put it in and the problem is still there. any suggestions?