I had joked a few times about louder exhaust sounds making your cars faster and handle better, but here comes 180bandit to confirm it.
But condescending remarks aside, I can see that sound is the missing ingredient in making Gran Turismo a total package. Between things like Shift's lurching camera, shaking, rattling and noise filled car interiors, and Forza's roaring exhausts, GT5 does come up several decibels short on that point.
But I have to quibble about it a bit. The over-the-top sounds and effects these two games use are just as bad to me as the racers that hype the sense of speed. Both of these are unrealistic and hurt the other games which strive for realism, like Gran Turismo. Forza 4 is particularly bad in this sense. You have the bot cars kind of muffling along sounding like the proverbial bunch of Hoovers in a replay, when your car comes ROARING into the scene with a V8 engine and racing muffler. The only problem is it's a stock 4 cylinder VW Golf.
This is a sin most of the fans overlook because... hey, it sounds so much cooler. But seriously, T10 has gone to ridiculous extremes with this. I mean, to the point that your stock Golf drowns out the tire sounds needed to help you hear when your car is edging into the lack of grip territory. I know many of the fans who have been with the series since Forza 1 are already dialed in and don't care. But since games like Forza and Shift have moved the goalposts into the unreal territory to one extent or another, it makes GT5 sound that much wimpier. And that's not just unfair to Gran Turismo, but every serious racer which uses street cars, which... well, I guess that's just Gran Turismo, come to think of it...
So, does Kaz just go with the flow and start hyping and distorting all the sounds to be like those other two games? Honestly, I hope not. I'd much rather Gran Turismo stay like this than give into the "sounds on 11" crowd. But what do they do, then?
I think they do what I suggested in my massive post a page or two back. Then there's what avens posted. And I have to say, dude, why did you white it out? It was a good post. I do think the things you mentioned are kind of corollary to the point though. Like, if you take a car in Shift 2 or Forza 4 for a spin and have all the assists on - which is probably what happened in the intro with the Ferrari race in F4 - I don't think it's the assists which hurt the experience. I was juiced after that, but when I got into the game, the new green tint in my glasses faded quickly. Now I understand that as you get into racing seriously, you eventually come aware of those assists. And kind of feeling like your dad has one hand on the wheel to keep you from getting into trouble, you eventually want to kick them out of the car and do it all without any "parental" help. Still, that's a little different from not feeling like your in the car to start with.
I think that falls more into the getting into the Big Boy's Game, serious racing based on FIA, WRC or whatever real world racing leagues, where you can't cut through flat grassy spots or slap on a Stage 3 turbo to win races.
Having said all I have in this thread, I have to yield to both the masses and The Master and what he decides in all this. Clinging to my soap box pedestal and yelling that everyone who disagrees with me is crazy is counterproductive, especially since I don't have a unique grip on the Truth Meter. Kaz is listening to this collective noise from us, the fans, and sifting through it all to see what has merit for upgrades to GT5, as well as how to build GT6. So mostly what I'm doing in threads like this is to say, "Okay, more noise, more volume, more shake, maybe some diver cam lurching. But just don't get too Hollywood with it." At least that's my intent.

Edit: and here, I posted practically on Slip's toes there. Two different if slightly in harmony perspectives on this.
To bounce off of his post, the world of GT5 is extremely perfect, like a scene from a Tokyo street in the morning, where everything is perfectly clean, painted and unflawed. It could indeed stand to have some messing up done to it.
So with that, I yield the floor and wish you all a Merry Christmas, and ask you guys what else you think would work.