2012 Chevrolet Silverado - Stabilitrak Light and P0304 Misfire

My 2012 Silverado is running like junk. It feels like a dead miss. Interestingly, the 'Service Stabilitrak' and 'Service Traction Control' lights came on at the same time as the Check Engine Light. Code says Cylinder 4 misfire. I swapped the plug and wire from cylinder 4 to cylinder 2, but the misfire stayed on 4. There's a clicking/ticking sound coming from the passenger side of the engine that sounds like a mechanical tap.