Broken bolt

If you end up removing the manifolds, the FIRST thing to do is SOAK all the fasteners down GOOD with a premium penetrating oil and that's NOT WD40. Use something like PBlaster or Seafoam Deep Creep. Soak them DOWN. I mean DROWN them. Then come back and do it again. Then let it sit a long while before you attempt to take it apart. I did that to mine and got every single one of them out without breaking a thing.