battery or ecu issue

I learned from this forum how to properly refurbish the original traction battery in my 07 and got a trouble free 3 more years out of it. Another module took a dump finally and I had already prepared as it showed symptoms by having a new nexcel lithium pack on the bench. Popped it in and, as advertised, went from 43 to 50 mpg. No issues on install or firing the car up and happily burned through a tank at around 50 mpg. Entire pack was well balanced in arrival and the vitals on dr prius looked great.
I then packed the car for a trip west. A few hundred pounds of vacation gear and a relentless headwind and hills for 700 miles. Before the wind started mpg was identical, then dropped sharply with the wind and hills. Averaged 34-35 through a few tanks. As soon as the crap was unloaded and it was back to daily suburban driving in the flats with no wind I expected the mpg I was accustomed to but I’ve put two tanks through it and have yet to crack 40 mpg average once.
The ice is insistent on charging the hv battery to the mid to high 60s % at all times, even under the load of a hill when it is needed most. More gas pedal will give me the amps if I get into it but as soon as I back off its back to throwing a few amps into the battery. Having watched the app for years on the old nimh pack and having watched it the first few hundred miles on this new pack with zero apparent difference, I can see something’s changed.
So I’ve got a brand new pack, internal resistance, temp, available power is all spit on, but something happened during that drive or perhaps coincidentally at the same time and this new setup is now worse than my old clapped out desert nimh pack.
I have disconnected the 12v pos/neg and all ecu connectors for half a day a couple times without change. I’ve forced the pack down to low 50 percent range to give some head room for ice warm up since it’s low ambient temps here compared to where I installed. It happily runs the ice to high 60s to 70% regardless and then occasionally keeps running to knock off some charge at a stop. Gets into the first green bar often. Has all the signs of an old pack but isn’t and has tons of power on demand.
So is this ecu or is this in the boards in my new blades?

 

It’s v2. Temps upper 50s to mid 60s. Been through many much colder winters which is when I had my highest mpg. Any temp effects were trivial relative to ac compressor effects in summer. The point is I’m confident if I pop the old pack in the trunk I’ll get 43-45 mpg driving it like a rental at a race track but some discreet event has occurred a few hundred miles after install that has the ecu intent on topping the voltage. Is there a memory capability in the module boards? Do the first hours or miles of use determine anything? Car is running absolutely top end everything 11/10. Getting 38.5 mpg no matter driving style now.