I use a HKS EVC IV and it is great. The auto calibration is fantastic. Two power runs on a dyno and its good to go.
You can save fuel by not pressing the right pedal too hard But that defeats the purpose of owning the line, doesn't it ??
You should call a certification engineer if you have any queries on the legality of anything. I know a good one, if you want the number send me a PM.