Had the heat-up issue in the early days but that was because I used Rx8 OEM radiator which could not cope-up with 1UZ, later on installed bigger radiator and never had any issue since then; also had the vibration issue, re-fabricated drive shaft and the problem went off. Although there's a very minute vibration at the speed above 135km/h which is due to reason as mentioned by Sammad_Kh and is absolutely bearable.You need to check drive shaft of your W124 or it could also be some problem with your mounting.It has nothing to do with the engine itself to what I believe.
UZ Family is well-known for its fuel efficiency, I have read many people getting more than 10kms/liter on highway driving in their SUVs even on full load and with low final gear ratios.I never took my car on highway otherwise would have been in better position to endorse that.Just for an instance here is an example from a Pakwheeler who used to get 10Kms from 1UZ.
https://www.pakwheels.com/forums/electrical-wiring-battery-lights/236651-1uzfe-engine-electrical-help
I am not sure about Hyderabad, may be the previous owner used to live there but it never had Electric Blue color for sure; Its originally Brilliant Black in color.
