FYI: OS X 10.9.4 Update Breaks Previous SSD TRIM Mod (OS X 10.9.4 released June 30th.)
After updating to OS X 10.9.4 via software update, I checked system Info and it showed TRIM support as "No". I usually prefer a download updater but was hoping that Software Update (a delta) would not overwrite the file (and undo the mod). Get Info on the file from 10.9.4 shows the version and date wasn't newer, but apparently my (modified) file in 10.9.3 was replaced during the update.
I then tried enabling TRIM again in OS X 10.9.4 using the same commands as before (via terminal) and restarted. TRIM was still not shown as supported. After 2 tries using the command line without success, I restored the IOAHCIFamily.kext file from a TM back I'd made after the mod in OS X 10.9.3. A restart and check showed TRIM support was back. (Normally I don't like to use files from a previous update but the mini isn't used for anything important anyway.)
Despite the file date/time/version being the same, 10.9.4 Software Update overwrote the existing file and the pkg was revised for 10.9.4 as TRIM mod commands had to be changed for replacing the SSD ID string.
Update: I later reinstalled OS X 10.9.4 from a D/L updater and used the new terminal commands for 10.9.4 to enable TRIM again. (Info on 10.9.4 added previous post on terminal commands.) After a reboot TRIM was again shown as "Yes" in OS X 10.9.4 System Info SATA listing for the Intel 520 SSD.