One thing I also noticed with the front bumper cam....depending on where the engine is on the car (front engine or mid engine), the engine is louder and quieter, respectively.
So for example...the Vette Z06...the engine can easily be heard, and the exhaust noise it makes is sweeeeet. However, with the Ferrari F430...the engine is a little more muffled, and I can hear it more in my rear speakers along with the exhaust, than I do in the front speakers...so I found that to be a nice touch in my opinion.
It really is an interesting mix of sounds though. Some cars sound really really close to real life, while others are just a little off, and others just don't make sense to me.
Another example, Z06 again, sounds almost identical. Go watch a youtube video with stock Z06 exhaust and tell me it doesn't sound close to the exhaust in GT5p. The Ferrari F430 is one of those that is on the fence. The tone is there, but in the higher RPM's, it becomes a little electronic, and not near as raw as the Z06. And then Viper GTS just seems to be too muffled in comparison of what I've heard, while the Viper SRT-10 sounds pretty close to real life....Is it just me, or does anyone else see it like this?