I can't help you with the conversion problems, noise, but I DO know who the author of the original car is. His name is Kris Winters, but he used the nickname 'Cougar' as an NFS author.
Nice to see the readme on the NFS3 car is still intact, but it seems his name was never in there.
(reading the other names mentioned in it is like a nostalgia trip
)
Nowadays we consider it a decent low-poly model, but at the time, a polycount approaching 2400 was almost considered too much. :p Notice the apology in the readme about the lack of low-detail carmodels and the warning about lagging on slower PCs. Different times, my man.
Point 2, yes, there IS an NFS4 version of it, but it's been a while since it was on any websites, and right now I don't know if I have an original ZIPfile on any of my backup DVDs. I DO have a separate Car.viv file of the NFS4 Cougar, as it was part of the line up of the original Detroit Muscle mod (veterans may remember that). I can get you the .viv, if you want.
I haven't heard of Cougar since 2000 or so, he used to hang around a bit on NFSCheats and the old TotalNFS (nowadays Racerplanet) and I doubt if his old email address still works, but I could give it a try, should you want me to.