P0400 is a diagnostic trouble code (DTC) for "Exhaust Gas Recirculation Flow Malfunction". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. P0350 is a diagnostic trouble code (DTC) for "P0350 Ignition Coil Primary/Secondary Circuit Malfunction".
Well, You bought a Lexus for it's quality and dependability among other reasons I am sure...Buy OEM parts and have a piece of mind that is not made in china...Sleep well 😉