I can't really tell if I'm getting a mileage increase with the Rokktech. Whatever the difference is (if any) is in the realm of the error from how well I top off the tank, fuel quality, etc.
One thing I DO know is the improved low-end torque. I had some pinging last fall and put the stock sensor back in to see if it was timing related. Eventually it turned out to be a dirty injector(s).
I had been driving about a week and turned left ahead of traffic and wondered what was wrong with the truck when I hit the throttle? It seemed sluggish off the line. Then I remembered that's how it was before the sensor and that I had left it off. Put the Rokktech back in. For my truck at least, I get a much smoother entry into torgue than without and I like it. Worth the money for me. BTW, I am cat-less and I think the Rokktech works better with that mod. My truck is noisier with the Rokktech.