2009 LT, I had the evap valve changed on top of my tank today after pulling the P0449 code. Also changed the solenoid on the intake manifold for kicks. I did had a P0302/4 misfire at the same time as the P0449 but it’s gone now, still changing that coil pack tomorrow. The coil pack was originally on #2 cylinder but moved it to #4 to check it. By the time I got home, less that 3 miles, the CEL light came back on showing P0420 & P0430 now. Maybe it needs some miles to sort of reset or clear out? I find it weird I didn’t get those codes until I put a new evap valve on. Ideas?