He has eliminated the downstreams (the ones after the cat, which don't affect mileage, or mixture, so his statement has no bearing on your situation.
)
You should be expecting mid 20's with mixed driving and a heavy foot. Cut it down to 3000rpm shifts (before the secondaries open up) and you can improve on that...
Highway's can see above 32 on a well maintained car.
Get that code number from Autozone when you see the CEL again. Post the number itself and we can greatly educe the guesswork of what to replace. (The 2.5 has 4 o2's. two upstream and two downstreams)
Ray
