My O2 sensor has been giving me a code. Some troubleshooting and a loud roar from the engine bay made me check the gasket out; especially after replacing the sensor. Taking the manifold off, I found lots of char-like soot outside of the gasket opening, so exhaust has definitely been escaping from there. When I first went to take it off, the nuts came off too easily, some I just twisted off by hand. One stud came out when removing the nut. Seems to have been screwed in and then soldered in, doesn't look like a weld. Taking off the solder I was able to screw the the stud back in quite well, so it has bite. When I put everything back together, I was able to get only 2 of the studs to around 35lbs/ft. The rest keep turning and or tightening. It is weird. As an example I marked one stud with a marker, the end that sticks out past the nut, and when tightening, it does not always turn the nut with the stud, as in, more of the stud sticks out past the nut, but then sometimes, it will turn with the stud. What's confusing the heck out of me, is that if the nut rotates clockwise, but not the stud, then it should be tightening it, if both the nut and stud turn, since, the stud is screwed into the engine block, then it should ALSO be tightening. In either scenario, the only thing that could be causing the behavior is stripped thread in the engine block, but by now, the stud should have fallen out, especially since when the nut turns, but the stud is still, it keeps pulling more of the stud past the nut. Either the stud should have fallen out, or the stud should have snapped off, but neither is happening. Am I mistaken on all this? What can I do, since I'm not reaching the appropriate lbs/ft. Also, can I replace the double ended stud and just put in a good ole bolt?