You don't necessarily have to retard your timing on boost. The early 930s did not have a timing retard function, full advance was set at 28*. Your timing curve will depend on how much boost you run, what your C/R is, fuel octane, and single vs twin plug.
I assume you have standard low C/R 2.7L with single plug and pump gas with maybe 0.5bar boost. Should not need to retard on boost, just tune it well.
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
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