I keep fouling out the #6 sparkplug. I just installed my new engine and can't figure out what is causing this. I thought I might have a header leak because black dust was above that cylinder so I replaced the header gasket and sparkplug and it started fouling out again after only driving it about 10 minutes. I looked at the sparkplug wire and it's fine. I have a new opti and new SVO injectors. A friend of mine shot a heat gun on that sides header before I replaced the header gasket and it was running about 100 degrees cooler (320 degrees). I'm hoping the new gasket fixed this problem but I don't have the heat gun to check. I don't think it's a problem with my new tune because it's only affecting 1 sparkplug. The rest of the sparkplugs look clean but the #6 is really black.

 

You can try to swap injectors, #6 can be leaky. Header leak will cause all bank to run rich. May be rocker adjusted wrong?

 

Thanks. I'll try switching the injectors around tonight to see if it might be an injector. My engine builder adjusted my rockers so they should be right.