bad spark plug
bad spark plug wire
Are the most common
Less common would be bad coil pack, swap #2 and #6 wires on coil, if new code is P0302 then replace coil pack
test #6 fuel injector with OHM meter, 11-18ohms is spec., it can usually be done without removing injector.
Last thing would be a compression test on all cylinders, see if #6 is 15% less than the other 5 cylinders