I have a 97 gsr and I have a fuel ratio gauge and it says im running lean.
Not sure I know what this means, and I dont run a o2 sensor cause if I do it just sucks my gas

 

what ecu are you running then? running with a new o2 would actually get you better gas mileage...that could be your problem

 

If your car is not tuned then you need that o2 sensor to run your car. your ecu uses a closed loop system. it takes info from all your sensors and adjust fuel accordingly. if you dont have the o2 sensor in then your ecu is "guessing" how much fuel to add, and the afr gauge your using is probably not the most accurate thing in the world unless its a wideband. running lean is going to eventually cause reputable damage to your engine. it uses a lot of gas when the o2 sensor is in because it needs it

 

Yeah im sure the gauge is off. And I have a pherable ecu. The gas mileage isnt terrible but I had put a new o2 put in because my old one was melted and it seemed like it was worse so I took it back out. So do I need to put it back in and then reset my ecu?

 

are your running a wideband o2 or just a normal o2? if its a normal o2 sensor then the gauge you have is useless. a normal o2 isnt capable of giving an accurate A/F.