I'm guessing you'd install them on your CD? That would be awesome!
I have always had a liking for the 300CD's, it's just something about having a two-door turbodiesel .

1. $$$
2. Engineering...solenoids, plumbing, etc.
3. Getting it to function smoothly
Wouldn't a VGT like on the new CDI's and TDI's also eliminate lag while allowing higher top-end PSI?
Just my 2¢

........I'm sorry, I just can't help imagining my 606 running twin turbos..

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99 E300 TD -- sold
01 540i 6 spd

Instead of all that complicated junk leading up to a GT2259, why not just use a single GT2259V? The same response time (if not faster) as two turbos, much more tunability, cheaper, more simple, more efficient, lighter, and more reliable.

Twin parallel turbos were obsoleted by VNT turbos. Sequential turbos are only useful if you are going for high boost pressures with a very large turbo for the high end boost.

Lol! Well you know what I'm talking about then. Yes, a variable may be the better way. Almost certainly cheaper and simpler. I think a GTV23 was about ideal.

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I suggest we solve high gas prices with environmentalists... unfortunately they don't burn well.
1982 300CD, 220K miles: This vacuum system will be the death of me yet! (OBK #26)
1977 F150 400 C6 2wd, 10.2 sec 1/8 mile with 2.75 gears.
1965 Mustang. Mostly stock... LOL!
2001 Ram 2500, cummins, 5spd, 202k miles.(girlfriends)

A VNT will build boost crazy fast. Unless you want to run more than 30psi of boost, I'd suggest the VNT route.

Here is the diagram you need:

Would be a lot simpler. I forget, what did you find the sizing of the your... Gt2256V was it?... to be?
What boost is yours set for?
When does boost hit 8-10PSI, wide open throttle, with the vanes fully closed?
What boost does it run as you pass 4000rpm, wide open throttle, with vanes fully open?

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I suggest we solve high gas prices with environmentalists... unfortunately they don't burn well.
1982 300CD, 220K miles: This vacuum system will be the death of me yet! (OBK #26)
1977 F150 400 C6 2wd, 10.2 sec 1/8 mile with 2.75 gears.
1965 Mustang. Mostly stock... LOL!
2001 Ram 2500, cummins, 5spd, 202k miles.(girlfriends)

Right now I have it set for 13psi. It's small for people wanting big power, but it's great for a fairly stock engine.

I get 13psi by ~2000rpm at full accelerator depending on what kind of clutch play I use. If you were to power brake with an auto tranny, I have no doubt you could get full boost without moving. I'll get full boost in every gear before I shift at ~2800rpm (Except 1st gear where I usually hit ~8psi.) If I wire the vanes open manually, I get about 11psi at redline WOT.

I can take this turbo to about 18psi if I had the fuel to use that much boost. The GT2256V would be great if you want 150hp. A GT2359V will get you to the 200hp range. The very rare GT2559V will get you into the 250hp range. If you want the most power, a huge GT37V like Brandon has will get you 300+hp.