So I was messing with .psarc update files for InFamous 2, and I found these files:
All of the files are about the same size range, almost 6MB each, so they all sound like different costumes/weapons for Cole. I tried renaming one of the costumes to "cole_default.xpps" and packing it into a psarc to try and install it as an update, but the game didn't even try to do so.
I am able to install the official psarc updates by putting them in hdd0:/game/BCUS98125/USRDIR/patch/psarc/ but if I install them like this, the game gets confused and won't load textures for areas too far from where I start the game, and I can fall through the ground in those areas. Most likely because I'm trying to install the patch without the updated eboot.
I think something in the official psarc's are telling the game that they are valid, and I think it might be i2.xpps, but I also think that i2.xpps might be the file that causes the game to load funny.