The idle up valve does just that, boosts the idle speed when the A/C is on or the power steering is used at idle. You set the idle speed (under load) per the FSM specs. I think it is something like 1000 RPM, with either the A/C running or when you crank the steering wheel while stopped. Exact speed is really not important, you just want to avoid bogging the engine down.

The A/C Amplifier sets the low cutout speed of the A/C, so you want it's RPM setting somewhat below the normal idle RPM. The A/C Amp cuts the A/C off if the idle speed drops too low. If you set the RPM too high, the A/C will not kick in properly.

So in short, idle up RPM a little faster than normal idle speed, A/C Amp RPM a little lower than normal idle speed. And neither of the above settings have any effect on normal idle operation of the engine. They only come into play when the A/C or P/S is in use at idle. The FSM does cover all this, but you need to look in all the appropriate sections. That is the normal idle is covered in the EFI section, the A/C idle part is covered in the A/C section and the P/S idle up is covered in the P/S section.