I agree with you to an extent. But the SLIGHT backfires that are in the game are nothing like what you and i showed in these videos.
And how can we be sure that the methods in that video are nothing "new". We (atleast i haven't) seen how PD records their sound? Like i said in another post, a lot of cars in GT5 use the same sound as multiple others, especially once you put an exhaust on.
All in all i think we can agree the sounds definitely need to be improved 👍.
The "backfires" were louder in GT4, and have been toned down, like everything else, for GT5. I'm not sure why. Overrun is a complex beast that is not to be emulated with a handful of samples, anyway - just listen to the wide range of tones that can come out of an engine with carburettors. Not only that, the first electronic fuel injection systems used on the F1 cars in the '60s retained some of the part-throttle fluffiness you'd associate with carbs. How do you reproduce that without adding in a "part-throttle" sound bank? Modern cars also have some very interesting, high-frequency fuel control going on that leads to very distinctive overrun sounds.
Anyone hanging around before GT4's release was treated to footage at Twin Ring Motegi of various recording efforts, including on-track recording of a selection of cars, but mostly static stuff (likely where the startup and horn sounds came from). I can't find many of the videos, but
this seems to be from the same event. The overlap in sample usage has nothing to do with recording method, and more to do with them not having really recorded "modified" cars (outside a few specifics, like that Mine's etc.) since before GT2. There may be a reason for that, but who knows.
Saying the sounds need improving is one thing, to start beating on the sound recordists and apportioning the blame is quite another. Part of the blame is possibly due to static recording not being effective at picking up the intake (I'm not sure if this is always, or ever true), but that doesn't explain why practically every car in GT5 has no intake sound, not all cars were recorded that way - the R8 is a great example: it was recorded on a dyno, but that glorious intake is totally absent from the interior (that's all you can hear in those things, it's great!).
The reason Forza's Ferraris sound "so good" is because the intake sound is mixed in with the exhaust for all views, so it actually sounds "better" than it does in real life!
That "mechanical noise"
is in fact mechanical noise, coming from the exhaust rattling (as in the C63) or practically singing (as with the F1 cars). That sort of thing is difficult to capture in a sample, and can be the very thing that betrays the looping at times. It's a dynamic thing that must be treated as such, but once you've got it working, you've got something to throw your "backfires" down for extra effect.