Good morning, Scotty! Greetings from Memphis, TN, and thanks for the informative videos. I searched the forum but could find anything close to my wife's issue. Recently, she bought a 2009 Chevy Silverado LT (Automatic Transmission, 4 wheel drive). The current OD reading is 270706. In March, she decided to drop in a brand new engine for AER. The truck had been running great! Then on 7/4/22, the check engine light came on for about an hour before turning off. My wife had me pull the codes on 7/5/2022 which showed (P0420 - Catalytic Converter needs replacing). On 7/6/2022, a local shop replaced the driver's side converter, and said the rest of the system looked fine. On 7/08/22, the truck would not start twice after being parked, then 15 or so minutes later it would. Both incidents happened after highway driving for about 30 minutes or so on the highway. On 7/8/22, the same thing happened again, but after 20 minutes of driving on the highway. On yesterday, 7/9/2022, I had the battery and alternator checked and the are both good. The starter is brand new. Could the Catalytic converter cause this problem? Or, is there something else going wrong? Thanks for any help you can provide.