I have found the best settings for monitoring LSM P25 with a 396XT.
Enter the hidden menu (press hold together with power on - the display blinks with 2 colors)
Audio AGC: off
Change mode from NFM to FM (func + 9)
in settings:
P25 LP filter: on
P25 adj mode: 8
P25 Adj. level: 200 (that way it starts on mode 8 wich is best for most systems)
Edit/Delete Message
If you are running the newest firmware, these settings aren't necessary... We've got numerous simulcast systems throughout the state of Michigan, just like Miami's, and with the latest firmware, the following have been working for us:
AGC: Off
Mode: NFM (Should ALWAYS be NFM for true Project-25 systems)
P25 LP Filter: Off (Only turn this on if needed, in VERY rare instances as it taxes the scanners processor and slows overall scanning performance.)
P25 Adj. Mode: 11 (Uniden's default setting with the newest firmware)
P25 Adj. Level: 50 (Uniden's default setting with the newest firmware)
Just for giggles, I went ahead and tested your preferred settings on the Michigan MPSCS system and the scanner could barely track the system with the "P25 LP filter" set to on; also, decoding was horribly distorted with the "P25 Adj. Mode" set to 8; and when set to "FM vs NFM" adjacent channel interference from close in sites and other transmitters becomes an issue; which isn't surprising since you're changing the receive bandwidth of the scanner to 25.0 kHz. instead of 12.5 kHz, which is what Project-25 are... Leaving it in "FM" also make the scanner have issues with local cellular sites in and around a simulcast system as well.
Just some thoughts from a state with ALLOT of LSM Project-25 trunking...