My '99 Si has been throwing out a P0133 CEL for a while now. I read around that it's a Oxygen Sensor Circuit Slow Response (Bank1, Sensor1)

I also read that it could be due to an exhaust leak. I'm pretty sure that's whats triggering the CEL. Are these exhaust leaks common on these cars? How expensive is it to fix? Bummer, as I was wanting to sell the car soon. I appreciate the advice.

 

Check for a cracked header, holes in exhaust pipes, and replace exhaust gaskets near or upstream of the primary O2 sensor.