Noisy and sluggish? Mine positively leaps off the mark very smoothly... Totally standard V6....
I regularly tow a 4.2t 5th wheel caravan between the North Highlands and the Algarve (total 6.5t). There are some serious hills in places on that journey, and you are 'pedal to the metal' to keep up. Sport mode, or even manual mode helps, as is reduces the tendency to to change up too frequently, and also gives more engine braking, which is good for going downhill.
I know several people who have the V6/Celtic Rambler combination - it is arguably a 'classic' set up for long distance/long stay camping. One friend had a remap done last year, and subsequently the truck went into limp mode several times when towing (blocked DPF) - and of course, in the middle of nowhere, abroad. On return to the UK, the supplier removed the remap and conceded that it was unsuitable for towing. My friend was told that there were now so many sensors, the software doesn't work well with a simple remap. They no longer offer the remap for those who tow. I suspect if you use your right foot a lot, you'd get the same result even you did not tow at some point.
My guess is that manufacturers will always spec the lowest possible DPF component they can get away with, especially the "less-than-premium" companies like Nissan, given what they think the typical, expected use is going to be. A remap, that includes more turbo boost and more fuel, is the equivalent of having a slightly larger engine, but your DPF, cat, EGR etc remain the same size and spec., not to mention the brakes, autobox, and general drivetrain not being beefed up either....
Many of my caravan friends would walk away from a used Navara that was up for sale, if they suspected it had been remapped.
On the other hand, if your truck is a second vehicle or a toy for fun use, and you didn't need to totally rely on it when a 1000 miles from home, I do get why you'd want to to tune it. I was the same years ago with cars (all petrol though)!
