A quick search pulls up this from the stickies section:
http://forum.ppcgeeks.com/showthread.php?t=42730
PST Tweaks:
First thing you must do is get your MSL. I wrote an app to make this very easy for you, more info on it
here. If you have problems getting your MSL, put your phone in flight mode and try again.
You can tweak your Slot Cycle Index (SCI) to make your phone poll the tower more often. This makes your texts and phone calls come through quicker. This setting is a trade off between lag (most noticeable when receiving calls) and battery life. The default value on our phones is 2. Every step of 1 adds 1.28 seconds to the poll time, so at a value of 2 it is only polling every 5 seconds or so. Most people lower this to 1, so the phone polls every 2.5 seconds. This won't affect battery life much in areas of good coverage, but may impact it noticeably if you're in a poor reception area. Your Access Overload Class (ACCOLC) determines your phone's priority on the cell tower. The higher the number, the lower the priority. Do note that 0 and 1 are reserved for emergency service uses, so DO NOT use these. You can ACCOLC's of 2-9, default on Sprint should be the last digit of your phone number.