Hello:

You can do a simple, but more conclusive test with real digital volt/ohm meter-- they are totally inexpensive these days! You do not need a fancy one...

With the car warmed up (after a mile or two of driving, with the coolant temp gauge reading in the middle), take your volt/ohm meter and set it to volts with the range set to somewhere around 1V. Pull back the boot on the cover on O2 sensor lead under the hood a little bit and touch the positive lead to the connector that you have uncovered. Take the negative lead of the meter and hold it to a good ground under the hood somewhere. You should see fluctuations from around .1 to about .9V, with a cycle lasting about a second or so. I would not be terribly surprised if the range was less for your sensor if it is in fact original. The other component that may want some attention by this mileage is the fuel pressure regulator. Both can have a pretty serious impact on your mileage and neither are all that difficult to replace.

There are generic 3 wire O2 sensors available from FCPGroton.com for less than $50 and genuine Bosch fuel pressure regulators will only run you about $36. That and all the work you have already done will ensure that you have a great baseline level of maintenance and tuning done on your car.

There is more exhaustive information on 02 sensor diagnostics and the like in the 700/900 FAQs, most of which is directly relevant to your car!

Good luck!
--
Herb Goltz, London, Ontario, Canada '92 245 w/102K mi