Do I need an O2 SIM?

[pgriffith]

I am throwing codes

P131 - O2 Sensor
P151 - O2 Sensor.

Autozone says my sensors may be bad. I just installed a cam, heads, intake manifolds and RKSPORT headers and Y pipe. Do you think its just the headers and I just need O2 sims?

[SLOWBRAEATER]

You cant use o2 simms on the manifold part of the headers, i wish you could, you use the simm after the cat

[SLOWBRAEATER]

does anyone know if you can use a simm before the cat? why cant you use them on the manifold o2s?

[96_maro]

The O2 before the cat controls your fuel mixture and what not, where the after cat one tells you if your emissions system is working properly(ie. too much flow trough the converter).