Hey Fellas i need help, getting ready to sell my car and every so often i get misfire codes, showing all 6 cylinders misfiring, and a random misfire code, but the car is not misfiring!!!

I changed the plugs in January, NGK plugs. just pcd, j pipe and an intake on the car, nothing more performance wise. This is my first Acura so im not foggy to common issues, can someone please advise!!!!

 

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if it's a six speed, it possibly could have been over-revved

or the cat's are clogged