I talked to the guy who wrote my tunes, and he commented on the late model drive by wire stuff at length.
The throttle in my F250 is a fly-by-wire thing no doubt, but it really is a torque on demand system. He said that it only allows a certain amount of engine power at a particular pedal position. This makes the driving experience smooth, but mostly I think it reduces emissions by building in a little "lag" time into the throttle, ie. a driver might "punch it" momentaritly, but not be so inclined to hold it to the floor for more than a few seconds on a regular basis.
Another computer trick the factory does is put a large delay in switching between closed loop and open loop. The factory tune would start a 10-15 second timer to open loop whenever the throttle was opened and high engine loads were encountered. With the aftermarket tune loaded and my ScanGauge hooked up, I can watch the computer instantly switch between open and closed loop by simply pressing on the throttle.
Gas engines don't get the big, wild hp & tq gains from a tuner like a diesel does. But just those two adjustments make a noticable difference in the power delivery your engine already makes stock, which equates in to a more "spirited" feel even with a 5.4L in a F250. The dyno charts on the company's website talk about ~25hp gains with the tuner on a 3valve 5.4L, and I guess I'll have to take them for their word on that, but I'm simply happy that my engine doesn't feel as lethargic anymore.
To answer Zach's question about the 5.4L + TorqueShift combo, yes, I have driven one and it felt a lot less powerful but I think that was because it had 3.73 gears. That was one of the main reasons I went with the 4.10 axles on this truck. I have yet to drive a 5.4L F250 with the auto and 4.10 gears; they're actually kind of hard to find in this area.
1999 Ranger 4.0 Sport --SOLD!--
2009 F250 XLT CrewCab ShortBed
5.4L / 6 Speed / 4.10LS