The SU-99 usually runs M,W,F evenings. Lately it seems to be heading west anywhere from 9 - 11 oclock. If you've got a scanner listen to 160.485 and you'll hear it get a form D west. It takes about an hour to get to Echo Lake Rd from Little Ferry Yard. The SU-99 will also always call clear of Butler as well, but you've got to be quick to catch it at Echo lake, which is only five minutes or so west of Butler.
As was posted previously, the SU-100 usually goes through real early 5-8am M,W,F or it will work in Sparta for the early part of the day and come east in the afternoon. Again, once it leaves Sparta, its about an hour (give or take) trip east to Echo Lake Rd. Hope that helps. Good luck.