This is Darin's supra =http://www.youtube.com/watch?v=WIkB6Zl1wc8
I made the same sound in my RB4 check it out it's pretty good

[url]file:///C:/Users/Acer/Documents/Azureus%20Downloads/Live%20For%20Speed%20S2%20Alpha%20Y%20Cracked%20version/data/engine/RB4_jto93.eng[/url]

with

[url]file:///C:/Users/Acer/Documents/Azureus%20Downloads/Live%20For%20Speed%20S2%20Alpha%20Y%20Cracked%20version/data/engine/Turbo%20Whistle2.wav[/url]

And
[url]file:///C:/Users/Acer/Documents/Azureus%20Downloads/Live%20For%20Speed%20S2%20Alpha%20Y%20Cracked%20version/data/engine/BOV1.wav[/url]
It sounds exactly like that with 1450HP in your RB4.