I had put some Techron in the tank and soon had a misfire on cylinder 4. Changed out all of the plugs and everything was great! Now about 300 miles later the car was ‘bucking’ every time I up shifted and slowly rolled on the throttle. It was driving me nuts and I questioned whether or not I was causing it with my foot input on the throttle. Sure enough the next day cylinder 4 is misfiring again, changed it and no issues, for a day, but now she’s bucking again! I guess I’ll be putting a new spark plug in #4 soon. Any ideas about what is causing this?