Phone Help with xperia arc s LT18i downgrade to android 2.3.7

Hi to everybody, well i bought an xperia arc s 2 weeks ago, and i update it to android 4.0.4, but i dont like it, its to slow and has a lot of lag, ive been asking in yahoo that someone give me the generic rom to downgrade it, this is my last hope, please, could anyone give me the generic rom to downgrade my xperia arc s, please,

The number of the model is: LT18i
Android version: 4.0.4
baseband version: 8x55A-AAABQOAZM-203028G-77
kernel version: 2.6.32.9-perf
BuildUser@BuildHost#1
build number:4.1.B.0.587

Please help me, give me all the stuff that ill need to downgrade my phone please