1) I'm assuming you're talking about the 9600 P-25 Trunked System
2) Are you sure it's trunking? (does your scanner stop on a freq and show a strength) - if not, you need to make sure you have the freqs in the scanner correctly and that the trunked bank is set up correctly. If you have both of those correct, and it's still not trunking, adjust your audio quality (hold "9" for a few seconds) and try truning again. It seems to vary per scanner and location as to what the audio quality should be.
Hopefully this helps a little - if not, please give specifics as to what the scanner is doing and what you are trying to listen to exactly.
Yes, the Austin 9600 system is usually very busy.