Misfire when hot, replaced everything I could think of... Options

[cv7713]

OK, been chasing a misfire for quite some time. The car runs great first thing in the AM but misfires once normal operating temp is reached. Misfires at idle and while driving. First, I have replaced all fuel and ignition components and all vacuum lines. I decarbonized the combustion chamber (MOPAR CC Cleaner, good stuff!). I have replaced the MAP sensor, O2 sensor, and some various wires that looked corroded. Stock 5s-fe.

The engine bay seems to be getting extremley hot! (but not overheating). Yesterday I pulled the plugs to see if they show any evident signs of wear and I was confused by what I saw. The firing end looked great (brown to grayish color), however the insulator on top of the plug was brown and blistered (burnt)?! Anyone ever see this? They are NGK plugs with the factory heat range. Also (not sure if this has to do with the misfire) but every now and then I hear a pop come from my gas tank. Is the "pop" just releasing pressure from the tank? Is it supposed to do that? Sorry so long, I am just truly stumped!!

List of parts replaced:
Fuel Pump, Filter, Pressure Reg, Charcoal Canister, EGR Valve, and injectors
Brand new distributor, wires, plugs, igniter, O2 sensor, MAP sensor, and even the ECU!

Could this be a bad cat causing the heat? Cracked head? Thanks for input...

This post has been edited by cv7713: Nov 9, 2007 - 11:21 AM

[cv7713]

The aftermarket seals were $24 for all four but they did not work. I do not know the Toyota part # or the price. Maybe someone here can help with that. I have an appointment today to have my injectors remanufactured by a guy in Sunrise. He charges $25 per injector and said it takes about an hour. He also replaces the seals with new OEM-type ones. I should have them installed by the weekend. I'll let you know....

Installation is pretty easy. I can do it in about 20 minutes but I have done this many times. If you want to do it yourself I can probably make a how-to when I do mine.