O2 sensors pre- and post-cat

[xxalexx at ix.netcom.com]

> If standard O2 sensors only work at a single O2 %, and the cat itself is
> changing the O2 concentration in the exhaust stream, and the ECU is cycling
> the pre-cat sonsor around its optimum ratio, then what does an ECU expect
> the post-cat sensor to be telling it?
> 
If you happen to see a 96 or later GM manual they give graphs and
limits and operation.  The ECU expects the CAT to release O2 at
a frequency. every 1 or 2 min?  If CAT does not put out enough O2
and car has less than 100,000 miles go to dealer and get a free new 
one.
alex