I added the AF1 and Xcal2 to my 03 Exp (4.6l). I also am running Royal Purple oil. Using the 93 performance tune, I certainly can feel and hear a difference in the performance. Definately more power, better shifting, accelleration.

Unfortunately, I really haven't seen any improvement in MPG. I was averaging around 15.5 before the upgrades, and am doing about the same after (with all the appropriate caveats - keep the foot out of it, drive the same speed etc.). I was really kinda hoping for just a few mpg's.

Two questions about further adjustments - (1) I read somewhere that shift "firmness" is actually slippage intended to prevent the driver from feeling the gear shift, and this is less efficient in terms of power consumption and usage. The implication was a firmer shift equates with less slippage and that equates with better use of power/fuel economy. I am wondering if adjusting the shift firmness would make that much of a difference?

(2) In my reading about MPG improvement, one of the biggest issues is drag due to form (at highway speeds; skin drag is more dominant at lower speeds). The 03 Exp is more rounded, but does have big mirrors and a roof rack. the rear end of all of them is very flat, which contributes alot to turbulence as the air flows over/under the vehicle and then tries to rejoin the airstream behind the vehicle. It is why submarines, airplain wings and boats have a tear-drop shape (and why some bullets are "boat-tail" shapped). My question is about the rear spoilers usually attached to the hinges of the rear lift gate. They are sold to keep the rear window clean (presumably becuase it keeps the air flow off the rear window). Well I was wondering if that spoiler would actually have the effect of reducing drag, and if so, would it be noticable? Would removing the roof racks help (I know they are a source of drag too).

Sorry for the long post. Just some of the many questions I am pondering. It is fun to experiment though!