Toyota Repair: Engine misfire, engine misfire, code scanner

Question
I have a 2000 Toyota Tacoma Pre-runner, 2 wheel drive, 2.7 liter, auto trans. For about a month straight I have been getting this pinging/rattling noise under my hood when I reach the speed of about 55 to 65 MPH.  This noise only happens at that speed. The truck doesn't really feel sluggish. I now have about 102,000 miles on it.  I also noticed that the check engine light came on several times last week when this noise started.  The engine light flashed about 4 or 5 times then went away.  The code scanner read "P0304 Cylinder 4 Engine Misfire". I'm only able to get this code as soon as the check engine light comes on. Can you please tell me what this noise is and how to fix it?

Thanks

Answer
The first thing that has to be addressed is to find out why there is a misfire on the number four cylinder.
The next step is to check the engine compression on each cylinder, the compression should be about 180 psi, if the compression is good check the electrical system, spark plugs, wires, if it all seems ok then I suspect that the #4 fuel injector is the problem, this is not uncommon on these engines, you may have to replace all the fuel injectors to fix this problem.