Re: Car misfires on Hot days???
Could be as simple as carbon build up on the EGR or even arcing between the wire and the engine. It could be as bad as a flat cam lobe.
You stated that you replaced the plugs and only checked the wires. I would replace the wires to make sure it is not that, since that is a fairly cheap replacement. Also take a look at your EGR valve to see if there is carbon build up. If there is clean it (duhh i know stupid to say, but some people will come back in and ask what to do next so it is better to assume you dont know).
Have you checked the coils themselves? It could even be a bad coil. There are manythings that can cause this, but these are the basics.