If you want a 200hp n/a d series your probably looking at spending more than $8,000 when you can build a turbo d that is capable of 250hp for $3,000. I think the y5 is more than capable of 200hp, the only thing different on a y5 is the roller rocker valve train and the egr valve stuff on the intake manifold. Injectors are also different but you will be changing those out for 200hp either way
This. There are so many threads on people asking about how to build a 200+hp all motor d-series or if it is even possible. I just read through a handful of them and guess what...not one of them actually achieved it. Some of them ended up scrapping the idea when they found out how much money and custom stuff is going to go into it and did a swap or ended up boosting.
Even the big dogs like Bisi have to drop a lot of dough and a lot of R&D to get that kind of a number out of a wee little d-series without forced induction or nitrous.
It's not that is isn't possible, it just isn't very financially feasible for the normal person that doesn't have access to one off parts and a team of builders that can stretch the dime.
Every step of the way in reading through posts, threads, and forums dedicated to this I have found that the only constant thing is that you need very deep pockets and someone that is able to do custom parts (manifold, cams, etc).
Google it. I guarantee you will come up with more than enough threads to dig through. It's been discussed for over a decade now. You aren't the first and certainly won't be the last.