alrighty! a last and further update to this thread because it is 100% essentially relevant:
I suspect this applies to all folks who are using good quality silicone plug wire boots and still finding they get burned up... not header brand specific, mind you...
in 2009 I bought a set of Sanderson CC3 ceramic coat block huggers. <- THEY WERE THE ROOT CAUSE OF THE PROBLEM FROM DAY 1 !!!
Later analysis of those headers found pinholes in several places, cracks in seams, and cracks on the lip of the collector flange end...
In addition to using shamelessly thin wall tubing, they also did not weld the tubes to seal them into the collector, they used some form of goop, which I have to tell you doesn't last very long!!! once this good begins to break down, it gets red hot in the centre, and promotes breakdowns of everything else...
which is why I believe the pinholes develop, and later cracks.
now you can blame mixture setups destroying headers, as Sanderson claims... you can blame improper exhaust mounts, as others claim...
I can tell you I have a set of unknown brand absolutely cheapo headers on my 77 corvette that DO NOT LEAK because they got properly welded to begin with...
Shame on you Sanderson Headers for using goop instead of weld, and thinner wall tubing than I've ever seen before on a header!!!
so to recap:
If you are experiencing problems burning up plug wire boots, your headers or exhaust manifolds are leaking. Pull them off, clean them up, and inspect them like you've never done before... You will find where the leak is in no time... Or you can also put a shopvac on blow at yer tailpipes, and use soapy water, for the easy to see crowd...