I disagree. I swapped out my 3.91? (87 turbo) for a 4.10 JDM diff. The turbo reached full spool LATER in the powerband with less load, and since I ran out of gear/rpm faster, I was spending LESS time in the powerband sweet spot, and this is even with a CT 57 trim. When the Torsen diff broke, I was much happier back to my stock diff. Big turbos NEED that load and time under load. With a really laggy turbo, I bet you'd only get 400 RPM worth of full boosting before you redline on a 4.30 (just my hunch, I'm not an expert mind you)
Perhaps for a drag-purpose only car, it might work out somehow, but on the street, it is annoying.