I've been using that since it came out, it works great. just don't use it on O2's they make something different for those. I just replaced the headers on my old Suburban, they had to be over 10 years old and the bolts came out like I put them in yesterday. That was steel bolts in aluminum heads. I change spark plugs about every 100k and I have 360k on it and it makes changing them so much easier.

The steel header adapter plates had steel countersunk Allen's, they have a 3/16 hex drive I believe, they all came out easily aside from one that I had to weld a nut to to remove. I used nickel permatex that's rated to 2400f but it was about 80% gone from all the bolts. Some remained on the threads that were deep in the heads, but the permatex on the bolts had been burned away from the bolts that go into the adapter plates as they get much hotter than the heads. The bolts that go into these plates are socket head cap screws, steel as well.
The countersunk face of the bolts I did not put much antisiese on, that's where they galled a little; on that face. I think it would have helped a little in this case but I don't think it would have made a difference over a whole season or more.
Im thinking about getting the flanges jet hot coated, or something like that. If anyone has experience with that I'd love to hear about it. I think having that countersunk faces of the flanges coated would help but I need a better opinion for antisiese in these high temp marine applications.

Countersunk bolts stick because of the surface area and conical mating angle. Try to give them a really good wack with a hammer to the tool if you don’t have an impact driver. If that doesn’t break the tension well, 30 seconds of blue butane torch will. Just be careful with fumes in engine compartment. Don’t want you to go boom. It happens !

I have removed a few zillion countersunk bolts from brake rotors and snowmobile secondary clutches. They all need to be whacked and : or heated to come out.

I totally agree, lots of surface area on the face. I tried an impact, impact driver and torched it, it just wouldn't let go. I still think I need a better / higher temp lube. You can see little bit of galling and a little bit of antisiese on the threads, these threads were in the head.

How long did you torch it ? I have to count to 30 aiming flame right at head of bolt. Anything under that they usually don’t come out.

Did you put antisieze under head ? If not, try it. I have not because brake rotors and cvt clutches. Lol

I didn't put any antisiese under the head, I'm sure that would have helped short term but I don't believe it would have held up long term, I need a better antisiese.

Okay. If you think so.
Doing quick search i found this possibility:
https://www.superior-industries.com/...oduct_167.html