I've driven multiple different model year FEHs, and noticed that in 09-12 models, the charge/assist gauge sways way further back into the charge range when using regen brakes compared to 05-08 models (including the 08 I own) that barely dip down at all. I also noticed the newer 09+ models also seem to be a lot more EV-happy even under modest city acceleration, whereas with the older models even lightly pressing on the gas will make the ICE fire back up again. The hybrid system just seems to operate a lot better and smoother as well, but from what I've been told it's just newer operating firmware/software. Is there really no physical difference or is it just programming (aside from the 2.5L engine vs 2.3)? Is there any way to "update" operating software on older FEH models?

 

I have wondered the same thing. I figured at least someone would be hacking or tuning the system like they are doing all the performance cars now. I have seen no evidence anyone is doing so.