I'm with Hillwood on the DPF, EGR, DEF issue. I'm with Eric and Boss Tractor on the idea of jacking the HP on the smaller NXs by tweaking the fuel delivery.
In fact, Boss Tractor must have been reading my mail.

I love my NX4510 HST Cab, and the HP is everything I need 95% of the time.. In fact, I even love the DPF system. But, every once in awhile I could use the additional 15 HP that Eric has on his NX6010. So, if I had a do-over, I'd probably go with the NX6010, which was only about $2K more at the time. It's my understanding that the engines are identical, and that the difference is programming for fuel delivery. If so, why not, once past warranty period (which is admittedly a long one)? :scratchchin:
Just asking rhetorically, as I doubt I'd actually go to the trouble of doing it.
BTW, anyone have thoughts on whether tweaking HP by upping fuel delivery would implicate EPA requirements? I'm assuming not, if the DPF system is the same in both models.