Watching with interest..................
Just a small note on your manifold design, since you have omitted the expansion joint on the regular manifold i suggest you keep the flange holes at the head pretty wide as it will expand and contract considerably, if you make them tight there is a tendency for the studs to get sheered off or maybe developing a leak.
In the past i had seen a tdi with fitted turbo on a mag, i belive it was some sort of french landy with a huge turbo, it had the most amazing exhaust manifold made, it looked like rams horns making a neat 4 into 1. Wish i could find a pic!
Regarding the actuator, you can get aftermarket ones with different spring rates according to the boost required, but you will need to fit the whole thing, funny it works by vacuum
Keep it up........
Grem