The game didn't slow down anymore like before, on Chenghou Project, so I can't pinpoint the exact reason ... maybe the PS3 was doing stuff in the background?
If I may, Chenghou Project: Feisar ship, go to #1 spot as fast as you can, to avoid all the middle fight, use barrel rolls and turbos (absorb the other items), should be #1 in the lap 2, if you are 3 seconds behind on lap 3, you can already restart. Once there, that's the hardest part: surviving, the AI is going to throw missiles, quakes and more, keep barrel rolling, and prey to receive a shield!