There was a time when mechanics tuned systems similar to tuning a guitar. Optimum timing, more or less fuel etc. Today the modern car takes care of all that many times a second. Most MBs now time each individual cylinder plus or minus from the rest. The twin plug motors even alternate which plug fires first and times each plug for optimum efficiency and temperature.
The only thing tuneable on the modern car is the alignment!
Bosch Master, ASE Master, L1
33 years MB technician