Do you even need to enable TRIM on a Intel SSD 320 series? I read this on the Apple discussion page.
"FYI, newer SSD's don't even need TRIM support anymore. All the work is done in the disk controller inside the drive rather than in the Operating System with software. "
"There has also been some confusion about garbage collection and TRIM. TRIM is ALWAYS preferred over Garbage Collection and will likely yield better results. If you have garbage collection, you don’t necessarily need TRIM, but it’ll probably offer better performance and there’s always a chance there’ll be a degradation of speed over time. Therefore, when using Garbage Collection, you may have to take the drive out and do a secure erase so that everything is re-marked as free space."