As far as I see it, there is no feasibly cheap way to safely do a "wet" Nitrous injection on a diesel without a completely custom intake.. and very expensive Nitrous setup..
Granted, but this is the TDI section
NOS adds air If you really wanted to add fuel when you add nitrous you could use propane or natural gas. Propane / Methane (NG) won't ignite on their own in a diesel, at least in the mix ratios you'd be using. When the diesel is injected and lights off it burns the propane/methane, so that is how timing is accomplished.
What if you made it inject after the main burn had already started?
Care to explain to me how m/ethanol is not a fuel?