You can remove scripts that use up memory and cpu from a jailbroken device. The scripts have the .plist file extension, and should not be touched unless you know what you're doing.
Older iDevices like the iPhone 3GS, iPod Touch 3G, and iPad 1 honestly don't really have the power to effectively run on iOS 5, which is a sizable part of the reason why two of the three aren't going to support iOS 6 (the other main reason being because it pressures consumers to purchase new devices). They were designed for iOS 3, but they also work perfectly on iOS 4. When iOS 5 came along, quite a few features were added (like Notification Center) on top of the already memory-intensive feature introduced in iOS 4, folders, and the older devices have trouble keeping up. If at all possible, I would suggest you downgrade your iPod to an iOS 4 release, but this is impossible if you don't have your SHSH blobs saved,** then replacing missed features with Cydia tweaks. If not, look into removing the useless or unimportant .plists from your iDevice using iFile, SSH, or some other sort of application that can search through jailbroken iDevices (iExplorer is an amazing application). Google is your friend.
Also, keep in mind the way RAM works on iDevices. Clearing it manually is essentially pointless, as the iDevice does so automatically whenever it needs to. Closing backgrounded apps is purely placebotic because iOS does this automatically any time it needs to. It's not like a PC that will just leave something running forever for no reason unless you close it yourself. Also worth noting is that backgrounded apps usually don't do anything in the background. They tend to just sit there, frozen. However, having a very large number of apps installed will cause slow-down, regardless of whether or not you even use them.
**I could be wrong in saying this, but can't iFaith rip any SHSH blobs from a device, assuming that device was at one point on that firmware and is susceptible to the limera1n exploit? I haven't used iFaith, but I know of its uses, and I remember reading an ambiguously worded article on it when it was released to the public. I think it can only rip the SHSH blob from the iDevice for the firmware version the iDevice is currently running, but I could be wrong.