o2 sensor and rough idling

[alex-evo]

Hey this topic mite have been talked about before.

On my ae86 trueno i see theres 2 sensors one near the top of the exhaust manifold and one near the bottom of the manifold. Its just that the bottom one is cut off and im wondering if i need it.

At the moment it runs abit rich as i can smell the fuel coming out of the exhaust and im worrying about emissions when i MOT it near late december time.

Also when the engine is warm or after a thrashing it struggles to idle properly it dips from 900rpm down to 5-600rpm and bounces back up.

Ive cleaned the filter, checked vacuum lines and they seems to be fine

any ideas ???

will try and get pics up on the sensors