As was said, electrical things are often temperature sensitive. As far as load, the coil really doesn't "perceive" the engine load. A lower voltage to the coil would cause a lower spark voltage out. However there is no suggestion that you have any battery voltage problem. A coil technically would "like" a slower RPM more than a higher RPM since it has more time to build up the magnetic field in the coil before it has to make a spark voltage out of it. However, it is designed to operate at the maximum RPM of the engine and I assume you are not running anywhere near that speed. Since you are not throwing a code I am wondering what the symptom is? The computer doesn't think there is a problem. If you were throwing a code then you could swap around the coils and see if the code moved. On my engine (M111) there are "dogbone" connectors under the coils which are often suspected of causing trouble. These constitute the wires in those locations. I don't know about the M104.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra