I drive an '05 Mazda 3, manual transmission. About a month ago, I accidentally killed the battery completely by leaving the trunk slightly open for a couple days. After getting a new battery, my car idles very noisily, making rattling noises, and constantly feels like it’s almost stalling when driving slowly or decelerating. It only stalled entirely once, in a parking lot. My friend thought this was due to the ECU crashing and trying to figure things out, so we put the car through an ECU reset procedure, but nothing changed. Any ideas?