<snip>

 Seems that
the bolt part of the flanges seems to be fine but the part in the middle
of the flanges is leaking air. I am using the metal one side gaskets
which is correct for this van. I am looking for ideas for what to do
next to solve this since I don't think the van will pass smog even if I
get the pipe leak fixed. The O2 sensor is adding more fuel. Do the
flanges warp? Can they be fixed or ground flat? Is there a sealent
that can be used on the gaskets that won't affect the O2 sensor?

William

There is an idea / trick that I have used to fix this kind of problem in the past. It is a simple idea, but kind of tricky to actually do. It entails filing / grinding the outer ears of the flanges to relieve some of the thickness, and make the gasket contact face slightly convex. That way, the center of the gasket is contacted first, and then the flanges pull down. The flanges will pull down and flex more than 1mm / 0.040" under normal torques! Good luck.

Evan Mac Donald

1984 Wolfburg
1985 GL 7 Pass.
1991 Carat Weekender
1972 Chevy P/U
1993 Bonneville