I used an egt gauge to tune my engine before wb's became popular. I tuned with it for about 15 years. I never had a blown hg or damaged parts while using it.
The problem with an egt is many things will affect the temperature. Placement in the exhaust system as well as timing just to name a few. Timing has a pretty big affect on temps. With reduced timing goes elevated temperatures.
New build in progress: Twin Gen 2 PT6466 352
Old combo:352 single 76mm turbo, 16psi, AOD, 9.41 @ 149mph, E85, 255/50/16 MT DR, 3500lb STREET car driven everywhere.