I forgot to write an update on what happened with my car. We ended up taking it to the Chevy dealership in town. After a few sensors replaced, 6 days and many confused mechanics, they finally determined that my computer was messed up and had to order a new one. Costed about $550-600. Definitely could have been worse but frustrating when we had already spent $250 for Tires Plus to look at it and replace the fuel pump ourselves. But car runs fine now! Yay.