I think the problem isn't really with PS3 performance, well, only inderectly. I think it's the CPU cycle priority that's ass-backwards when running GT5 online in multiplayer.
In all the race sims I've ever played, it seems that no matter what the framerate the GFX engine is running, the physics and netcode are unaffected. If the physics engine runs at 1000hz, or 100hz (or fps, same thing), the framerate you see on screen won't possible affect that because the physics engine takes PRIORITY. You could have a huge dip in GFX FPS, say down to below 15FPS, but it won't affect your laptimes or latency because the CPU cycles are there for the physics and netcode no matter what, and if the laptimes were affected, it would only be very slightly.. like hundredth of seconds.
It seems like that in GT5, PD coded it so that a hit it GFX performance can directly affect the physics engine and netcode negatively. This seems like a completely ''rookie mistake'' made by a team inexperienced in programing netcode.. EDIT- (that won't take or listen to outside help. Sound familiar?)
This also explains why the the physics are different online when netcode for multiplayer is being ''added into'' the equation. Off-line there's no netcode being run so the physics are solid. It also explains why it only happens with a lot of people in the race, the more chance GFX framerate performance issues are more probable. It also explains why it happens to people in the back of the pack, their PS3's have to render more cars (more cars in front), so more chances of GFX performance issues affecting netcode/physics.
I think what PD/Kaz have done is given the GFX framrate priority over netcode and physics engine performance in some circumstances. I'd take the GFX performance hit any day over having inconsistent physics online! It's a no-brainer.
It's another one of those WTFPD moments for me.
And I have noticed this from DAY ONE. I specifically remember GT5P having some pretty big GFX framerate drops online with a big field of cars online, more than the same amount of cars in a race offline. That FPS drop didn't affect physics though, like it can in GT5. In GT5P the netcode was correct though, which allowed for GFX framerate drop not to interfere with netcode and physics FPS. It all makes sense. I miss those GFX FPS drops in GT5P now, because online multiplayer in GT5 is FUBAR.
EDIT
To prove this theory, run 16 premium cars until problem is obvious, then everyone switch to standard cars. I bet problem disappears. All go back to premium cars... problem will magically reappear. This should prove my theory.
