Out of 9 studs, 1 came out without effort, 3 snapped off and I had to weld a 3/8" nut to get them off. My first time doing such a task and I'm glad it worked.
Other 5 studs put up a hell of a fight.

 

What a PITA, but well done on the fix. Have not crossed that bridge yet & if I do, Ill remember that trick

 

Did you try a stud extractor?

 

I did not, I used the double nut method on all of them with lots of spray and even a small amount of heat. But the 3 that broke where very weak, didn't take much force .

 

Hmm saltbelt state? Or is this common on the 4g63

 

Salt state, overall the car looks good though
Could the hood vent contribute to this if the car sat outside from the previous owner?

 

On DSM's this was very common. Some owners got to be real pros at installing thread inserts. I don't hear much about the Evo engine having this problem. In your case maybe age or possibly warpage of the manifold.

 

Ya I ordered some arp stuff so hopefully I don't have to deal with this again, the female part of the thread looks good but I may run a tap through it just to clean them up?

 

I did the same thing with getting ARP stuff, guy who installed them was surprised how easily the old ones came out. I'm guessing that's due to the PO replacing the manifold at some point.