Put Diesel Locomotive 2's SFX into the Diesel Generator 2
Assuming that Diesel loco 2's power-train is a hybrid diesel electric (diesel engine+alternator makes electric motor go vuuuUUUUUUUU), it'll make more sense for the DieGen2 to have similar sounds to it.
Why? It'll incentivize me to use DieGen2 more often with those beefy sounds, as i like the way my factories sound generally (specially while being afk).