The PS3 only supports up to 5400 rpm so even if you get a 7200rpm drive it will only spin at 5400rpm. Most likely something went wrong with the installation process try deleting the data and reinstalling it. Also if you are jailbroken that can cause some slow downs.

Also if the re installation doesn't work i recommend running some tests on the drive to see if there is any damage or bad sectors, and it might also be the game in the sense that it needs a patch.

 

Anyone else having some slow downs in certain parts of the game?
It does not happen everywhere.
I have read others having slow downs also but maybe because i got the full 41gb version and not the 3d rip version.

 

Not quite right. a 7200rpm drive spins that way regardless. The problem is that the ps3's interface limitations mean it usually won't take advantage of the extra speed it affords, and it also runs hotter, which isn't good for either hard disk or ps3. And it's only been with Gran Turismo 5 where the extra speed of an SSD has actually been useful, with install/load times generally cut in half with that game over a standard hard disk.

That said, if I could afford it, I would do a hybrid-hard drive like the Momentus XT in my ps3 to get some of that extra I/O speed and still have disk space to spare.