> Would you not expect some scaling of failure into the 50/15 test
> considering the severity of failure in the 25/25 test ?

Maybe. Those cars can be sensitive to test procedures.
I always let them run @ 2500 for 3 or 4 minutes before testing, I had
a much easier time getting them to pass that way.

> After researching some , would you expect a Oxygen Sensor
> malfunction or something else ?

I hate to sound nebulous, but... maybe..
O2, map, coolant sensor, tight valves.. there possibilities are almost
endless.

> Can the original O2 sensor last 18 yrs ? * The O2 sensor is the
> original :}

Er.. um.. maybe
Yes, I have seen plenty of O2's last a long time.
As another poster suggested, it's time to get your car someplace
*competent*
Ask your friends, call the BBB, call AAA.. find someone with a track
record of 'very high quality'.
Dont shotgun it with cheap parts, it may work, probably wont.
At least 3/4's of the problems I see mentioned on this board stem from
someone trying to save money....
Good luck, and I hope this helps.
Ben