i have also been wondering this as i come from the import tuner side of things. i have always had my ecu's tuned for my mods and it make a world of diffrence to have things properly tuned. i am thinking of calling up Power Enterprise as they make a little thing call the Camcon. it is used to control the VVTi/VVTLi and it also is a a/f controller. i think a stock truck with out i/e using the camcon to control things would make a huge improvement then just i/e without the camcon. the ecu's of all vehicles in the US all have teribble a/f ratios that is why a little ecu tuning always help. the VVTi on a 5.7L with a little bit of tuning =

jeff