i have a honda and acura performance handbook i bought down at barnes and nobles... it says that with a hot ignition and performance headers installed, there wasnt enough gasses left over in the cylinder to cool everything down and it melted the plugs. in his case, the problem wasnt the headers, cuz honda cpus can handle leaner mixtures of air and fuel, but it was really the ignition system, cuz it was so darn efficient that it burned ALL the gas.
now he says that you should address the lean problem before you get too far along adding performance parts. your plugs are going to show the signs of detonation or a hot engine before anything else. this guy in the book said the best way to handle the lean prob is to install bigger injectors OR improve flow thru the intake system (ie a new throttle body and intake manifold).
i know all that poo is confusing, so let me just tell you that i have a cat-back exhaust, air intake, and headers and i dont have anything to regulate my fuel or increase the amount of fuel headin into the engine. my car runs good and the plugs look fine. so i dont think that you need to worry about the fuel. tackle it a little later.