>... is the NRE unit with green and clean engines generating more visible exhaust ...

If it's your imagination then mine seems to be seeing the same thing. Though it does seem that most of it's coming from two of the 3 engines, and if those 2 are running at equivalent to Run 8 but the third is back a bit (6 or 7) then some smoke's possible from them (cf. typical trucks - haze or smoke on the governor but not so much if backed off a little). But then the particulate filters are supposed to catch that right?

If this hill with these trains was the use case for the new locomotive specs, then somebody blew it. They definitely need the full C-C units.