The FAQ for Black Chocobo that sithlord48 linked to in this thread, which describes how to get edited saves working on PS3/PSP, seems to be deleted. It says "replaced with New Wiki Page", but I can't seem to find that page. From what I can gather, there is no way to get an edited save file working on PS3 without the help of a hacked PSP.
I got it working on my PSP (I haven't tried going to the PS3 yet), I'm running the US PSN version of FF8. Here is how to do it; if you have a different version you might have to make some changes.
1 ) You need a hacked PSP (I'm using a PSP-1000 with 6.60 PRO-C)
2 ) Install the
CWCheat plugin
3 ) After creating a save file in FF8, open the CWCheat menu (hold Select for a few seconds)
4 ) Go to the Memory Card Management menu
5 ) Choose "Save Memory Card [1/2] to Memory Stick" (choose whichever one has the save file you want to edit)
6 ) Copy the file from the PSP at /seplugins/cwcheat/mc/SLUS_00892-0.mcr to your PC
7 ) Edit the file in Hyne, and save it with the same file name
8 ) Copy it back to the same folder on your PSP
9 ) Load up FF8 on the PSP, go into CWCheat, and choose "Load Memory Card [1/2] from Memory Stick"
10) In FF8, save again, this will write the hacked save file into the protected .vmp file.
If you want to play it on your PS3:
11) Transfer the save game from the PSP to your PS3