Hi new to the forum. I recently got a 2002 grand prix 3.8l non supercharged. Ive been getting a engine misfire code p0300 and p0304. Ive changed out plugs and wires, put in new coils also. I only get the code,at highway speeds 65 to 70mph im completely stumped at this point. Anyone have this issue or know what i can look for? Thanks in advance.

Sent from my SM-J700T1 using Tapatalk