Cylinder #4 Misfire on 1996 Toyota Camry

I have a check engine code that indicates a misfire in cylinder #4. I've already changed the spark plugs, wires, distributor, distributor cap, rotor, and the fuel injector #4. I've also had the pressure checked for all cylinders; all were fine. None of this has solved the problem. I noticed that every time i cleared the check engine light, I was fine for about a few days and then it would come back on minutes after i turned on the car; it has never appeared while driving. I do not know where else to look and i do not want to continue driving my car with a check engine light. Please help.

Asked by for the 1996 Toyota Camry
Is the code PO304? Does the engine sound like it has a misfire at idle, does it run rough. I have replaced fuel injectors on these, check the valve clearance (they are shim adjusted, a tight valve will cause a misfire) and check for a vacuum leak at the intake manifold gasket or a hose off the manifold near number one runner at the manifold. Another possibility is the EGR being dumped primarily into #1 cylinder if the other EGR passages are getting restricted not such a Toyota problem (common Honda problem).
what is an EGR? I'm having the same problem, check everything that was basic for ex. spark plugs, Coils, injectors, switched injectors and coils, but i did notice a leak coming from my intake manifold, I had also done a compression test, cylinder $ 1,2,3 reads at 170, cylinder # 4 reads at 120, you think the faulty gasket is causing cylinder #4 pressure to be that low?
I eventually had the entire head replaced... And that obviously eliminated the problem....
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lots of problems with carbon causing initial start up miss fires. as the engine warms up, the miss stops. you need someone to run a top engine cleaner for the valves. worst case is the head has to be removed and de carboned.