The Highline package was only available on the highest-trim E32, the 750iL. This means that all Highlines have BMW’s flagship V12 engine, codenamed M70. This is a 5.0L engine that makes 300 horsepower (220kW) and provides more than sufficient smooth acceleration even for a heavy car like the 750iL Highline. Torque is abundant, making passing at highway speeds a snap. In fact, when BMW made this engine, they realized it makes the car so fast that it may become dangerous. That’s why the 750 was the first car in the world to feature an electronically-limited top speed (at 250km/h).
The M70 engine is composed of two 6-cylinder SOHC banks with fully-independent engine management (ignition, fuel, etc.). It has 2 fuel pumps, 2 relays for them, 2 crankshaft position sensors, 2 fuel pressure regulators, 2 ignition coils, 2 spark distributors, and even 2 ECUs. The two banks are synchronized by an “EML”, which takes its signal from the throttle pedal and controls the two throttle valves. Incidentally, this is the first production car in the world to employ “fly-by-wire”, i.e. electronic throttle control.
It’s interesting to point out that the M70 engine was the basis for the engines that BMW made for some iconic cars (even more iconic than the 750iL Highline): the S70 engine in the BMW 850CSi and the S70/2 engine in the McLaren F1!