02 4Runner Idle Speed Adjustment

I have a 02 4Runner. Can someone tell me what the normal idle speed rpm should be when the transmission is in Drive? Does an rpm of below 600 still considered normal? Is there a way to adjust the idle rpm so that the engine will idle at around 650 (or higher) when in Drive? My 4Runner idles at around 700 when the transmission is in Park or Neutral but idles below 600 when in Drive. This could be the reason why I'm having a bit of a problem with rough idling. Please see my other post titled "02 4Runner rough idle." The idle goes back up when the A/C is turned on.

I believe that there's an idle specification of 700 rpm +/- 50 for 4Runners (warm engine). Does this specification apply only with the transmission in Park/Neutral or does it also apply when the transmission is in Drive?