o2 sensor

my 1g dsm has an a/f gauge. all the sudden, it stops working (one light is on at all times) so i know that the wiring is ok. gas mileage is bad, around 15-16mpg. but i am boosting a lot.

could it be that the o2 sensor is messed up?

btw i also have really bad idle surge

It sounds like you have more problems on your hand than you can fix at once. Vfaq would be your best bet right now. As for the bad MPG, you can try replacing the O2 sensor and probably your fuel filter would help. Fix any boost leaks if you any also.