The electronic boost gauges are reputed to be inaccurate. I know that mine never matches with the vacuum version that replaced the clock.
Boost Addiction - honestly, I have it under control
1989 911 Turbo Cabriolet
Mods include: Kokeln IC, GHL Headers, Hooligan muffler, Modified K27 7200, BL WUR, LC-1 & XD-16, Bilstein Sports (4), TRG sway bars, Oversize torsion bars, Strut brace