Thanks, very interesting.

At 11:18 PM 3/16/2013, Dennis Haynes wrote:
>... the Cat and O2 sensor failing together is usually due to a common cause.

Just to clarify, I don't know whether mine failed together.  My O2
sensor failed two years ago, right after passing smog.  It's possible
the cat failed then, or anytime since.

>There was a deflector shield that I bet is missing.

Is that something I can look for?  Photo?

>Since you have a modified engine there is probably increased
>compression and you may also have the ignition timing over advanced.

That could be.  I have noticed what I think is some pinging in high
gear at full throttle going up a modest hill.  That went away when
Van Cafe tuned the engine six months ago, but now it has returned, so
I must reduce throttle or gear down to prevent it.  I don't know what
might change the advance over time, but it may be time to adjust it again.