I adjusted my idle up a hair when I installed a new throttle body.

 

My '99 idles at 550 in gear. Park/neutral 650.
Sometimes slower when the iac valve sticks here and there.

Question on idle smoothness: Will a set of Denso plugs stop the intermittent lean misfire my truck has always had since new. (its not constant, just a shake and then a definite miss if you idle it for longer than about 3 minutes. Truck has 17,900 on it. I always put it in gear to keep it less noticeable.
Still stock.

 

550 rpms.... no, 700 rpms.... no, 450 rpms.... no, 600 rpms.... no, 500 rpms......... Damn!