The O2 sensors should be toggling up and down from 50-900mv. If they are at 450 that's a lean condition and the pcm will dump fuel but never satisfy the request.
Ur better off unplugging them.
Be sure the o2's are case grounded style. Sounds like the wrong o2's maybe.
No o2's working means no closed loop means no trims working.
What do u mean exhaust not complete?
If the o2's are too close to the open exhaust they will read lean.