Originally Posted by Mitco39

Thats not entirely true. I have seen the inside of diesel engines on farm trucks driven by old farmers with nothing out of the ordinary in terms of build up. I mean you always will have some but nothing to affect performance a noticeable amount or anything like that. Surely nothing like that picture. I suggest deleting the external EGR where ever possible, its just not a good setup. Most new cars just have a internal EGR by changing the cam degrees with respect to each other.

I bet if there was a way to turn this off on the Z you would see both fuel mileage and power gains from it. The Z does not have external EGR system on it, so it only leads me to believe it is controlled by the VVEL.