So your problem is a misfire on cylinder #6. Does the engine run rough, showing that its a real misfire? If so, i would start doing a compression check. Could be that a rocker fell off and the respective valve is not opening anymore. Instead of doing the compression check, you could directly remove the cylinder head cover (rh head as seen from drivers position) and check if the rockers are in place. Did the engine overheat recently?
Besides this, it could eventually be a wiring problem, or a problem with the PCM.