Im off to Digitrains next week to buy a chip for my Ford Railbus kit build. Any thoughts please on sound files? I am assuming that there won't be a sound file for these, so I guess im looking for a good equivalent. As I have never heard one it's obviously not a major issue. I am thinking of the petrol simplex. Im thinking petrol engine, manual gearbox, underpowered and rattly. What other considerations might there be? Any alternative ideas?