talked to my mechanic and a die hard dodge mechanic and they were saying the O2 sensors can make a little bit of difference in gas mileage but so minimal that you can't even calculate it at the pumps.....best look elsewhere....changed my O2's out and im still getting 8-10 mpg on a 5.9 4x4 sport and the truck runs great, im looking at modifying my existing air intake (keep it stock tho) and possibly a muffler with stock sized outlets, and the TB upgrade (fastman) For the air intake, i just so happened to look at one in stock at my truck store----the diameter of the part that fits on my TB is actually smaller than the one that is stock so I am thinking high flow K&N and some modified tubing into my fenderwell and I will have just as good as airflow system as those 200.00 ones, without the chances of pulling any hot air from inside my engine compartment 9 which hey even with a heatshield you do...

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priced those o2's there about 80 bucks apiece . I think I'll hold off and look some of the options you mentioned