What kind of mileage should I be expecting from my 92305/T5 with 125,000 on it? It just had a new o2 sensor and cat done as well as a full tune up.

I pretty much have the same configuration you do and with the 3.08 gearing in the rearend and a light right foot I've gotten over 25 mpg on the highway going a steady 70 mph.

I got 19-20 mostly city driving on my bird.

Well it seems the best I've gotten is 21. So I must be doing something wrong. Any suggestions?

Check out doing some of the TBI mods and adding an open element air cleaner.

That depends on what kind of driving you do. Mine gets an average of low to mid 20s just putting around back and forth to and from work. That is maybe half and half city/hwy driving. Maybe a little more hwy than city. If your driving is split like that with maybe a little more city driving, then that is probably just right. When I get up to ~70mph and cruise for a whole tank I can get up around 27 or 28 mpg. If I flog it around town and make a bunch of passes at the drag strip I'll see mid to upper teens.

So now that makes sense. Usually it is split like that and I've never really ran straight freeway in the car. So I usually see about 16-18 around town.