My stage II is really awesome in the sound dept.however...when I use the headset (which I do use fairly regularly) everything works perfectly. When I don't use the headset the radio maintains power but it is a crap shoot whether or not I'll get audio out of the speakers. I have tried the speaker switch in several positions, moving,not moving, smooth pavement, bumpy roads. So far I can'tfigure out what causes the problem or what solves it. Help!

 

Verify the harness connectors to your SII amp, and the 35-pin Ultra harness on the radio are properly seated first. Failing that, I'd be quick to blame the speaker toggle switch (assuming you're pre-'14). Without sticking a meter on it myself right now, I forget what gets continuity in each position. But, the dash panel switch harness plug uses pins 9-12 for the speaker switch.

Pin 9 is power, Pin 10 is a lead to the radio, Pin 11 is another lead to the radio, and Pin 12 is ground. In each toggle position, it'll be one of the following cases:
pin 10 shorted to 12/ground
pin 11 shorted to 12/ground
or neither shorted to 12/ground

Do a little diagnostic work on that before you go deeper in troubleshooting.