So I am not gonna read another 3 pages on bashing intakes. So if this was posted already I apologize. There are plusses and minuses with K&N. Do what you feel like doing. But if you dont have the cash for a new one off the shelf and other mods to make it beneficial, just stick with the factory ford intake filter and pull your silencer. The removal of the silencer will be the greatest gain possible.
The o2 sensors are in the exhaust and have nothing to do with your intake, what you see is the MAF sensor and PCV valve hose. Just make sure there are no leaks in the intake tubing (whatever mod you choose to go with) after the MAFand you will be fine. Someone mentioned exhaust and I didnt see where you asked about that, however if you wanna mod exhaust, flowmaster 40's are great for our v-6's albeit a little loud, if you prefer mellow go with flowmaster 50 series or MAC mufflers. if you dont mess with your cats, your o2's sensors and engine tuning will need no modifications.
What I will recommend if you do have the cash is the MAC longtube headers, offroad h-pipe, flowmaster 40's and an SCT tuner. you will have to extend the o2 harness but this just involves splicing 3 new wires lengths of 6 inches to each sensor.
Just my 20 cents.