Hate to be the bringer of bad news, but most of the comments will not improve mileage.
NOTE: before you just start to say something, go to "ecomodder.com" THey have a list of "65 things you can do to improve mpg". click on it, read it, look at the proof, look at the sources.
THis is a serious site if you really want to improve mpg
1. If you did not run a "a-b-a" or at least an 'a-b' test when you installed a part, you can't honestly add to the conversation.( how something feels doesnt count.)
A-B-A Testing: Drive car for 15 minutes before, take a run on a fixed distance (7-15 miles), run at a set speed(50-65mph), run up and back w/ out the modd to establish a base MPG, then immediately install the mod and do the run up and back. You now will be able to factually state if the mod helps your vehicle.
2. CAI will not/can not improve MPG. Period. Warm air improves. More hp does not improve mpg.(see ecomodder)
3. Runv Nitro in your tires. Nitro does not fluctuare with road heat. so you are at the correct psi all the time. Don't leave you tires at 33psi. Go to 39-41psi. That's what i run daily and when I'm on the road longer than 2 hrs, I run by Radial Tire Store in Sacramento and go to 46psi. (see Ecomodder.com before making comments)
4. THe key to high mpg is low rpm at cruise speeds. THe 02 Q45 is blessed w a 2.76 rear ratio, the 03-06 and all Ms are 3.XX(not sure the exact gear.) THe recommended tire on the 02Q45 Sport is 245/45/18 on the 18x7.5 rfactory rim. I run a 255/45/18. At 62mph I am at 1824rpm.
5.Taller tires does not mean go uot and get 20 and 22 rims. each pound you add is really 4lbs when it is spinning AND the more wieght you put on the uotside effects the enitire suspension. At the same time if the new rim and tire is slightly taller and wieghts 4 lbs less, the you have removed almost 50lbs from the moving wieght.
5. the TCM(TRANY BRAIN) adjusts to your driving style. the harder you drive the less mpg you will get, even when you try to drive easy on one trip. THe TCM is already trained. I will tell you that I drive for mpg so my tcm IS tuned to get good mpg.
6. I always like hearing talk of the 'restrictive intake' and the "restrictive exhaust". come on. 4.5 liters = 273 cubic inches. you've got 340hp!!! and the 3.5 and 3.7 are pushing 300??
THese engines are finely tuned. Yes, there are marginal gains at he top of the curves on hp, but hp does not equate to more mpgs.
7. Underboby panels. the tubulance created by a ruogh underside can affect the drag by as much as 30%. So keep the stock panels under there.
8. when your on the road keep tthe mpg screen on. "Play beat the mpg"
9. Ecomodder will tell you that the best mod for better mpg is to "adjust the NUT behind the wheel"
10. Finally, since no two drivers or their cars are the same OR the roads and speeds the drive, it really doesnot make any sense to say "I get 17mpg on a fillup or on my screen." There isn't any practical discussion that can take place. But if you say, "I get 20mpg at 65mph over a set disctance", then you can have a conversation about the difference that cause it. I don't check my mileage around town because I know it will suck. But I bust my but to get the best possible mpg when I 'm on the road, because that's where I can really make a difference.
I consistantly get 27+mpg on road trips.