I'm having the same speedtweak problem on LiquidSense 3.2. I use Terminal emulator, enter "su," then enter "speedtweak.sh" or "st" and it tells me that it's not found.
This isn't a good time for me to switch ROMs, so I'd prefer to stick with LiquidSense (though it sounds like others really like Thundershed, too).
I found the default kernel in liquid sense 3.2 did not respond to the commands in terminal like st.
But after installing the Imoysen kernel afterwards through recovery I then was able to type the commands in. After you install the kernel check the phone settings and then choose about to see the version of the kernel you are running. My guess is that you were not updated to the latest version. Also before installing the kernel clear dalvick cache in recovery then flash kernel then reboot.