well im confused now - to nads or not to nads, that is the question ....

[Hodge]

To their credit, Nissan came to the party and gave me a new engine, but alas, i got nervous, and dumped the car and jumped fence for a while - went to the dark side

Wow. I'm so surprised to hear a good Nissan dealer story ... Good on them.

Anyways
Evil Twin summed it up perfectly.
I'll just add the following...
I held off for ages on any NADS on my CRD, because I was reading that CRDs "don't need it", and Nissan has finally fixed the grenading on the CRD's. I call bullshit on all of those.
I finally bit the bullet and got some gauges. It was shock and horror when I saw the factory EGT temps. But they are supposedly normal, as evil twin said, CRD's run hotter, I don't know why. And the boost, well the factory boost control is just shit-house. It's a just a boost yoyo, up and down, and there seemed no explanation as to why it does it...
So NADs train began. Blocked the EGR, and the EGT temps dropped by about 50 on average, especially cruising. Then I got the needle and dawes valve fitted, and that fixed the whole boost yoyo thing. The boost had an awesome linear curve and the car just behaved so much more better. This also dropped EGTs a whole lot more all around. Then the factory prone to leaking, IC, finally leaked..... And that was replaced by a tig welded unit, and dropped some temps again. Catch can was added later on too.
At the end I had a car that behaved and felt so much more better. Lower EGT's, very nice stable boost, oil stayed cleaner longer...due to EGR blank.
Really IMO, it's a no brainer.

Edit: Also added the chip & exhaust, which also gave the car a new meaning again,