My car seems to hesitate below 3k, but only somtimes...

If i give it about 30% throttle in lets say 3rd gear, it will barly move until it hits 3k then it throws my head into the seat, right at 3k...sounds like its bogging below that and it doesnt pull hard at all...

Can this be caused by somthing with my A/F? cuz my O2 sensor and ecu are acting up throwing the famous code 43 and i have changed the o2 sensor and i still get the code every once in a while...

I have posted many threads on this, and no one seems to know whats going on, anyone have any idea??

Thanks