My hubby bought me an 02 Outback 4 weeks ago. Has 190K on it. Ran great for 100 miles then CEL and Autozone said code was a catalytic converter. This weekend the Battery and Brake light came on together. Researched and suggested alternator. I pulled into autozone and they said my battery was bad, since it was 3 yrs old I replaced it so they could test alternator. They said the alternator was going out so I replaced that and put on new terminals as well. Then it started randomly hesitating for a second. The car bumps and the rpm drops down and then comes back up so fast you almost cant see it. It will stall occasionally and it seems random, even with acceleration. I figured it was time to replace the CAT and took it to my local muffler shop. They said it looks great and isnt the issue. They ran it for codes and said it didnt have a code for the Cat anymore. Still hesitating and CEL. Went to a different autozone and got these two codes: P0604 Powertrain Control Module Random Access Memory and P1518 Starter Circuit Low Input. Im so confused. The stalling started immediately after we replaced the alternator, battery and terminals. Help?