A 1.0 bar spring is generally not recommended for use with a stock intercooler due to the possibility of detonation. An aftermarket intercooler should be your first upgrade.
Keep an eye on that VDO tattletail boost gauge. In my opinion they are junk. The tattletail needle can be stiff, binding up the boost needle, and eventually will break (like mine did).
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