Exhaust leak???

EDIT: sorry peeps it was an exhaust leak.. nothing wrong with the cylinder #4...
doug thorley headers suck... change the gasket twice and still leaks..the sound is coming from the last hole from the header closest to da firewall... the new thorley gasket I used was too thin, the napa gasket makes the noise even worser so I just put back my old thorley gasket the right side only & the noise came a bit quiet, I look at the old one & it looks a bit thicker than the other 2 gaskets I used, dunno if that made the difference... any of u guys had problems with this header...

Reset the valve lash and tighten the valve cover by the book Sometimes if you tighten up the VC to much it will make excess noise

Thanks 3tcRob for the reply.. I probally was gonna do the valve lash on my day off and see if that was the problem.. I seen that info on a 4x4 forum saying that if you make the VC too tight it'll make noise, it said to just loosen the 4 VC bolts alittle and the noise should go away..well I let u know whats da deal..

Its hard to troubleshoot without actually having some hands on experience of the noises and symptoms but my 2 cents worth I'll throw along.
If the valve cover was over tightened and hitting, pulling the #4 plug wire should make no difference, the rockers are still moving up and down.
You ruled out the exhaust leak already, too tight exhaust valve causing popping out # 4 cyl?
Worse case scenario, bearing or piston problem on #4, you mention the noise goes away when the #4 wire is pulled, typical of a rod knock, you unload the cylinder by cutting the spark. Hopefully its something simple and not internal. Good luck.

yeah hopefully it ain't internal... if it is then I probally just rebuild it... but right now Imma do a compression check and re adjust my valves if the problem still occurs then that cylinder is shot....

Could be a pistion oin noise or a spark knock as well wich will all go away when spark is pulled