2008 Dodge Avenger 2.4L P0301 Misfire: Diagnosis and Budget-Friendly Fixes

I own a 2008 Dodge Avenger with a 2.4L engine. About two weeks ago, my wife noticed the vehicle began lurching while driving home. We took it to an auto shop where they replaced the crankshaft position sensor. After pickup, the car continues to display fault code P0301 — indicating a misfire in cylinder 1. Despite replacing the spark plug in cylinder 1 and swapping the coil pack from cylinder 4 to cylinder 1, the issue persists. What's unusual is that the vehicle runs smoothly at idle for extended periods without triggering the code. However, when speed reaches approximately 15 mph, the P0300 misfire code appears and the check engine light flashes. We've added Techron to the fuel tank and refilled the fuel with no improvement. Given my limited budget, I'm seeking advice on the next steps: should I investigate the fuel injectors, mass air flow sensor, or EGR valve? I don't believe the catalytic converter is faulty — there's no rotten egg smell, which suggests sulfur emissions aren't present. Any guidance on affordable troubleshooting would be greatly appreciated.