Well, first of all let me tell you guys that as like many of you, I´m a GT fan for life. It is really cool that at last someone discusses such important topic like the sound in GT. Like most of you, I have noticed how this feature is very dissapointing in what is supposed to be the Ultimate Driving Simulator. First was GT1, with its fake engine sounds(there were like three engine sounds only), that nobody cared about since by that time, there was nothing like GT. GT2 brought all of us the maximum experience in racing sims in that time, and it was beautiful to see that most of the cars had "realistic" engine sounds, and you could notice that diference in, lets say, 75% of the cars. Then it was GT3...No complaints, except for a few cars (v8 race cars with the "vaccum cleaner" engine and others), but I was expecting that in GT4,things were going to change for good...GT4 came and not only I was dissapointed on the small downgrade on the grafics, and the harsh driving physics, but along came the same fake engine sounds from the previous two GT´s. I notice it not imidiatly, but only when I completed the American All Stars Championship(I think it was), and got the LM Camaro...I almost cried when testing the car expecting a roaring V8, I got...yes...the racing vaccum cleaner...after that, with alot of dissapointment, I discovered that only like 25 percent of the cars sounded like there real counterparts, and the rest were recycled from the previous titles...Be cause of this, I coulnt enjoy most of my favourite cars like the C5 corvette, the old Viper(GTS, not SRT10), the Sallen S7, and many more who don´t even get close of how they sound in real life...GT5P came to the market and I got it even before I got my PS3...It was a jawdropping experience, but after alot of playing, I noticed the same problem. Even if the cars sound really nice on the sound fx and the different possisions of the camera, they are the same horrible sounds from previous GT´s, and not only that, even having my PS3 with optical cable directly to a 5.1 Sony Bravia theatre, the sound of the wind is too much, and on the chase camera, cars sound terribly weak . As like many of you guys, I cannot understand why if Mr. Yamauchi states that he is such a perfectionist, he cannot get this right...Other thing is that when you modify a car in previous games, when changing the exhaust, the engine sounded even worst. For example: Try putting a racing(or semi) exhaust on a Camaro, and it will instantly change to an inline six cylinder!! Come on!! Even NFS gets the engine sounds right!! If you change the exhaust on a V8 car, it still sounds like a V8, but louder!!! And its NFS for crying out loud!!!(nothing against NFS. I had them all) I really hope that on the final version, we get at last what is keeping GT from being the Real Driving Simulator. I´m not expecting mind blowing FX but at least make every car sound like they have the engine that they have...I´m a car guy, and having a corvette that sounds like a vaccum, is like going to a musseum blindfolded...
To El Drifto and DonZonda:
You guys are right! The R8 not only does it sound weak, but in the first pages of this discussion, I was reading that the R8 was being recorded for GT5P on a press show, or something. Thats not true...If you guys have GT4, please undust your PS2´s(or force your PS3´s) and play the game. Go to Audi and buy the RS6...listen to the engine sound...I know that cars have similar if not the same engine block, but COME ON , Polyphony!!! Its the same sound efect! the only diference is that the turbo effect has been deleted in GT5P!
For some the world is not enough.
.The sounds make alot of feeling even for the sense of speed, you don't move faster but it feels faster when your car scream like in reallife. When i hear the BMW M3 in the cockpit view ... I am about to cry in GT5P... 
rologue is missing the grunt, while PG4 is over-exaggerated.
