i've been running my power fc with the o2 sensor turned off almost every since i've owned it. it seems that i got worse gas mileage with it on and i noticed if i watched the injector duty while maintaining a speed, it would fluctuate some. when i turned it off, i got better gas mileage and the injector duty stays perfectly flat at speed. i was just wondering if there's any downsides to this?

 

No downside really, lots of PFC owners do it.

 

You don't need to have it on if your Airpump is removed.

 

okay, cuz the car runs a ton better with it off. i didn't know if it might compensate for lean conditions sometimes or not

 

I dont believe the PFC reads the stock sensor obove 1500rpms or so. I could be wrong though.