2016~2023 CX-9 slower after dealer visit

Or this (well hopefully not, this looks like a bigger job to do)


Some customers may complain about a poor acceleration and rough idling or the CHECK ENGINE light ON with DTC P0301:00, P0302:00, P0303:00, P0304:00.NOTE: Only turbo engines are applicable; non-turbo engines are NOT applicable. In most cases, DTCs P030X stores, but sometimes not. Sometimes the CHECK ENGINE light does not recognize this engine concern. This is caused by the variable valve in the exhaust manifold seizing and causing the exhaust port to become hot and the exhaust valve seat to wear unevenly, resulting in compression leakage. To eliminate this concern, the design of the exhaust manifold has been modified.

Thank you! Do I simply take this to the dealer and ask them to check?
you could check for the first TSB yourself, for the second one they would need to check the stored codes to see if there are any and do a compression tests.

But yes you can tell the dealer you are experiencing the same symptoms as this tsb. Bringing a copy with you help. If you have a good dealer they would know right away about the TSB, but not all of them are great. Your issue might not be that specific issue though. It could be something else entirely l.