And the prize goes to..., perhaps if I (thr) hum along Doug?😊 (see reply to Martin for answer) It's real hard to get just the right sound to match a model (the sound units I have are not too bad) but there must be ways of doing it without having to spend lots of money on complicated sound units with set programmed sounds. In the case of my sound units, they are real engine sounds, programmed to be proportional on internal SD card but they don't quite match the model). A lot depends on the internal volume of the model (resonator), sound unit and speaker/placement.
The search will continue for a cheap alternative.
JB

She's not a turbo!