Sensor 2 is after cat and is 99.5% for emissions / keeping converter efficient.
The weight on the system is VERY small.
PCM has noticed open circuit voltage and has flug the code.
No worries man.

Cat has been deleted, didnt specify when has said straight piped. Its all crappy welds, plan on replacing the cat back and throwing a cat on the car so I can get passed emissions.

Although when I look at my fuel trims they are very lean, is this because there is only one O2 sensor. The exhaust manifold is cracked and it revs up and down on a cold start. Not entirely sure there is a vacc leak but it's a high possibility. Also havent seen it ever go into boost even when free revving up to 4k rpm (have been fairly gentle with her)
Thanks for the quick response!

Missing rear o2 will not cause lean fuel trims.
Even moreso since the sensor is gone and the PCM knows it.

Def take care of the exhaust issues.

You'll have best luck passing emission when all the mechanical stuff is fixed & working. A cracked exhaust manifold will let outside air into the exhaust gases and can cause a false lean conditions. You should replace or fix the the manifold which will give more accurate O2 values. Turbos don't build boost free revving, boost build when the motor is under a load. The O2 after the cat does not effect performance, it's only to monitor the cat & check that it is in good condition for emissions.

Thanks for the clarification! Havent taken it on the road due to the maintenance is very lacking at the moment. I'll get everything fixed and then see how it's running then.