When replacing the exhaust manifold bolts with S.S. this may only be a slightly longer time before the problem reappears. The problem is the cast steel manifolds that expand and contract with the heat cycles, causing the studs to slightly pull from the heads, and if the S.S. is not of good quality, they will rust and start the same problems. Using PB Blaster, or Kroil oil should greatly easy the pain of removing the studs. When removing the studs, I have found that about half of them come out with the nuts. Soaking the heck out of the ones that don't come out, usually helps them be removed. If the are stubborn, use a small pipe wrench or large vice grips to work them back and forth, and they should come out. The constant heat cycles and water intrusion is what usually causes the bolts to break. Most of the manufactures leave plenty of room to work on the headers, you may have to remove a front tire for more room and comfort. Sometimes an impact wrench helps loosen the nuts/studs.