Questions & or Observations about the GTEL

I have noticed that the Turbine runs @ 4860 in game, according to the manual it should be running @ 6900. Anybody else notice this?. Also My Notch indicator stops working above 50% and the engine does not seem to respond to those throttle notches. Have I maxed out the power of the Turbine @ 50 % load meter shows one tick off the white indicator in the green. Most all these Observations were done hauling 50+ loaded cars up a steady 0.09% grade. It just seems like the engine is not running at full power. 1st I have made sure the brakes have been released/ still not fully understanding the Advanced braking but working thru it... The turbine is spooled up and running very efficient until about 50% throttle.. Just curious if anybody else has noticed any of these things..... (Long Live the exotic's )