This is how I fixed Low on Space Message
First. I resynched my data with my pc and backed up using the Asus software.
Next. I downloaded both root program and Titanium Backup. Rooted phone first then used titanium. Made sure backup was saved to sdcard then factory reset.
After factory reset. Download Titanium again and run a restore. Everything is back and low space warning message does not reappear. Do not know what it cleaned up but it had been bothering me for months.