what can I look at to fix my misfire in cylinder 3 p0303 code?

Question

I have changed spark plugs checked boots, fuel injector, and for vaccum leak and they all were good.

Answer 1

Could be a bad ignition coil (the car uses a pack of 4) it will have to be checked. 

I would pull the coil pack out put spark plugs on it, lean is against the metal part of the engine and crank the engine and see if coil 3 is firing