Well guess what? I, who advocated welding the manifold, now a year and a half later the manifold is leaking in a non repairable area and I now need a catalitic convertor which I replaced at the same time as the manifold repair. With the large leak before the O2 sensor, the sensor read a lean mixture and richened the system to the point of taking out the cat! Now I have to deal with buying a manifold and then a new cat!
I hope this helps anyone with a leaking manifold and a cat that is still good. <img src="/forums/images/graemlins/zombie.gif" alt="" />