Article: https://dustrunnersauto.com/vq35de-vs-vq35hr/
In total upwards of 80% of the parts were changed. All the changes of the HR ultimately made it more fuel efficient by upwards of 10% and allowed it to make more power and offer a wider torque band. That being said, the DE definitely isn't a bad engine and at the time the DE came out it was a pretty awesome V6.
The only downside to the HR is that it's more expensive to buy one second hand compared to a DE, but that has more to do with perceived value and availability, and it kind of proves that the HR is the more valuable and better engine. That being said, the DE could be argued as the better engine for forced induction applications because it's simply cheaper to replace the engine if and when it explodes.
https://www.nissan-global.com/EN/DOCUMENT/PDF/IREVENT/PRESEN/2006/060824_IR-VQEngine_Eng.pdf
https://www.nissan-global.com/EN/DOCUMENT/PDF/TECHNOLOGY/technology_overview/VQ_E_070802_X-1a-02.pdf
https://www.nissan-global.com/EN/DOCUMENT/PDF/TECHNOLOGY/TECHNICAL/VQ35HR_EN.pdf
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