If your engine is a bone stock '81 (300HP) Euro with headers and 1.0bar of boost my guess would be a peaky 330-340HP at the crank. The reason I say that is because the stock turbo and stock intercooler are holding back the potential gains of the headers and boost spring.
A new aftermarket turbo and intercooler would really wake your car up, possibly another 30HP worth.
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