if im reading your problem correctly, your talking about the three studs that are part of the cat that bolt up to the exhaust. if this is correct, i had the same problem putting on my cat back two days ago, all three seized and broke the heads off of every one. (even after i soaked it in PB Blaster for about thirty min. Hate to say it, but i had to drill out every broken stud and replaced with three stainless bolts with lock washers and nuts. Its time consuming, especially if you got a shitty 12v cordless drill that only lasts for about three min. You could always be lazy, and buy a new cat! lol i probably would if i had to do it over again