VQ25dd are just as easy to modify/tune as the VQ25det, they are in effect the same engine, using the same cam actuation, but the DD has special swirl chambered pistons and high compression. If you were happy to run e85 you could still boost it, the rods etc should be good for some big power (same as the turbo rods) All the turbo gear off the det would bolt on...
Don't discount it as a performance base, I was planning to run my spare DD in a turbo race car not long ago and the Siamese runners intrigued me.