I'm curious if in the 96' country with the 4 liter if the computer will automatically adjust the Air to Fuel Ratio or if I will need to have it tuned? I know if it's running rich or lean for a while it'll blow the valves.

 

That's what the O2 sensor and MAP sensors are for. The O2 sensor monitors the air fuel ratio and adjusts it accordingly to factory specifications to keep the pollution to a minimum. After 80% throttle, the MAP sensors adjusts your air fuel ratio. If you have an adjustable MAP sensor (which can be built or bought), then you can fine tune your air/fuel ratio to either save a little gas or gain a little oomph.

 

is that the front O2 sensor or the back O2 sensor behind the cat that does that?

 

what about for a 87 cherokee

 

It's the upstream O2 sensor (the first one) that monitors the air/fuel ratio. The downstream O2 after the cat is just to monitor that the cat is working efficiently. An 87 is a Renix system, but still the same concept. It should have an O2 sensor and a MAP sensor that perform the same functions as the sensors on HO engine. On the Renix, the MAP sensor may look a little different.

 

Renix only has an upstream O2 sensor!