These are my priority cars, to have their sounds changed:
1. Mclaren MP4-12C - It's a Twin-Turbo V8, not a vacuum cleaner

2. Enzo Ferrari - Sounds like it's missing 4 of it's cylinders, literally
3. Lambo Murci - PD, it doesn't have the same engine as a Gallardo

4. Ferrari 330 P4 - Same as the Enzo, sounds like a V8
5. Audi R10 - A diesel shouldn't share the sound files from a Minolta, which themselves are incorrect

6. The Ferrari F1's - Completely messed up gearing, and too slow gearshifts. The F2007 in Prologue was near-perfect in this aspect

7. RedBull X2010 - It sounds like a V8 at 18,000 rpm, in reality it should sound closer to this:
<a href="http://www.youtube.com/watch?v=OxVpOfWyjHg">YouTube Link</a>
8. Formula Gran Turismo - The specifications state it's a V12 spinning at 18,500 rpm. It should sound closer to this than a 4-pot

<a href="http://www.youtube.com/watch?v=VY2ZudHWIUw">YouTube Link</a>