How are your applications and scripts are defined? E.g., If you have 1 IVR for 200 stores, and they all use the same script, then did you create 200 apps, or 1 app with a wildcard trigger, and use the dialed number to set variables for the store? One takes up a lot of memory, the other does not.
Try making your script file sizes as small as possible, because even if you can't consolidate scripts and apps, you can at least make them smaller and leaner.
Check how you are using the variables in your scripts. E.g., Are you reading in large amounts of data from a database or XML document and then holding that information in memory for the duration of the call, or are you dumping it as soon as you're done with it?
EDIT: Removed the order of tasks, as it's not that important.