2009 toyota matrix cylinder 4 misfire

My 2009 Matrix having a cylinder 4 misfire (obd2 code
P0304). I replaced all the spark plugs, swapped all the
coils, replaced all fuel injectors, checked the resistance
and voltage on the all the injector plugs. Everything I did
something, the same code kept coming back. I just
recheck my spark plugs again and #4 already have carbon
fouling (the plugs are brand new and I installed them 2
weeks ago). I also did a vacuum leak test with smoke and
didn't find any leaks.