A lot of great responses. Thank you all very much. I appreciate it. So to answer some of the questions, I drive the trucks exactly the same. My foot is just as heavy on the Denali as it is in the Escalade. The displacement between both trucks is the same. Only difference is that Yukon has the l92 and the Escalade has the l94 with AFM. I was under the assumption that I would have better gas mileage since it automatically switches between four and eight cylinders but I guess that's all just hokum and fairy tales LOL as far as calculating gas mileage, I wasn't running off what the dummy screen tells me. I'm basing all of this on distance traveled and how much the needle moves on the gas gauge. As an example, I live in Illinois and a round trip to Kankakee from Chicago is pretty close to 140 miles. The Escalade left me at a quarter tank while the Denali will only run about half a tank. I have the short body Denali not the XL so I do have a 26 gallon tank in each truck. At least I think I do. I need to do a physical inspection on the Escalade. Once I'm down to about an eighth of a tank, it only fills up with about 15 to 16 gallons which does lead me to believe that there is an issue with the floater. I am changing all the sensors because the truck is new to me but it does have 121,000 miles and it is 14 years old. I don't know when the sensors were last changed and I figured a refresh won't hurt. I just installed and cold air intake and all the sensors are on order. I do plan to replace the stock muffler with a Magnaflow straight through bullet muffler and remove the cats. The headers I'm going to replace because the current factory manifolds are rusted beyond belief. I don't think I have any leaks as I'm not throwing any lean codes. I think I'm going to do a smoke test and see what I get out of it. I did notice that the oil filler neck is pretty loose and it might be a source of air intrusion. I do understand that these trucks are heavy and it's also a big displacement V8. I do a lot of long distance driving so my fuel mileage should be better in the Escalade. That's just an assumption and a poor one at Best LOL I'm going to drive around for a few days with the new Cai and see how it does. I'll post updates. Again thank you all for the responses.
Also, the Denali has full exhaust, no cats, headers, c a i, high flow water pump, all aluminum three row radiator. So it runs cooler and has a more free-flowing exhaust.