Scania DC16 V8 & Opticruise G-Series Revision

This mod overhauls the Scania DC16 V8 engines (DC16.121, DC16.122, DC16.123) and the Opticruise G-Series gearbox for the Scania R/S NG by SWISSCAT, replacing the stock engines. Key changes include:

• Idle speed set to 550 RPM with adjusted rev limits matching the V8 redline
• Optimized automatic gear shift points to take advantage of the V8's massive low-end torque
• Smooth and realistic 13th gear (Overdrive) engagement at highway speeds (85+ km/h)
• Realistic high RPM behavior during engine braking for improved cooling
• Revised retarder steps matching real-life Scania Brake Management logic