Well, I suppose you could copy the vehicle and engine files into my mod and copy and paste the sound config from the engines you want the sound from, but It'd be better to create a new .zip entirely. I could take a look if you want.
Its quite hard to explain, but if you have a four cylinder engine, and you look at some sounds of it in waveform, you will see groups of peaks in fours. I crop these at different RPMs and vio la
i still have the same sounds i put the sound in my sound folder and my vehicle's in the vehicle's folder
why? just put the zipped file in your mods folder like every other mod. no need to tamper with the files