David,
Unfortunately, PS2 files can't be downloaded on PS3 chips. You'll need to find a PS3 file on the MTH website that will fit your desires. Sorry to say PS2 and 3 do not mix.
You can install a 3V PS2 file in a PS3 locomotive, but not the other way (unless MTH has changed something along the way). PS3 has enough memory to hold the PS2 files, but a PS2 board doesnt have enough to hold a PS3 file. I've noticed that within a run of locomotives, there are often 2 different files. If you look at the file names when you download them, compare the files from all the roadnames in a run, maybe another road name has a more acceptable horn.