I ended up taking the car to a buddy who runs a private auto repair shop. After driving it, he felt like it was a MAF sensor even though it wasn't throwing any new codes. Since he had the luxury of being able to return it, it was easy to try. Sure enough, it took care of the problem; been running perfect for a few weeks now. About 5 years ago, a remanufactured MAF was installed, so this time I opted for a new Cardone sensor. Problem solved.