i have a 98 legacy outback with 77 k miles on the car. the check engine light is on.  
the car was computer diagnosised that its 3rd and 4th cylender was mis firing.  what can be causing this problem 
I already replaced the coil, plugs and wires  and still no change 
  
if any one has an suggestions on what to do next would be greatly appeaciatated  please help  i need to take the car to school in two weeks so it would help if i get help asap....   thanks