ok 2 weeks ago my stang ejected a spark plug so i went ahead and put a perma plug in it which is basically the same as a heli coil. so far it is holding fine and i was wondering if it will hold up to some boost, and if so how much. never had to do one of them so i dont know their limitations.
If it was done correctly I'd imagine it's as strong as, if not stronger, than the original threads.
One thing you might want to keep an eye on is heat on that plug. Since you've added an extra "thermal resistor" to the heat path for that plug -- the insert -- it may effectively be a fraction of a heatrange hotter than the other plugs.