For a 930 (or 965) I totally agree that you cannot justify the project. Modern turbos with the right combination of headers, fuel, timing, and gearing have zero lag.
As an excersize in experimentation and mechanical creativity it would be an interesting indevor.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8