My d15b2 in my ef hatch seems to be in limp mode won’t rev past 3500 rpms and cuts fuel. before going into limp mode it was having inconsistent misfires the only code that appeared was code 1 for a 02 sensor also my dizzy is new any ideas of what it may be?

 

O2 sensor could be bad and would be an obvious one since it was giving the code for it. it could be an exhaust leak at the manifold, before the O2 sensor, or right at the O2 sensor which lets oxygen hit the sensor making the car think its super lean and causing the ECU to dump a ton of extra fuel making it not want to rev at all and run like crap.