I have a 98 that has 150K+ on it and it idles better than my 2006 with 25K on it. The 06 has idle rough (comparatively) since I got it. I''m not sure if it just idles at a lower RPM or if it''s really missing/sputtering.

Any thoughts?

sure, one of the first and most common problemns is probably a bad coil. In some cases the coil is good and the spring and resistor inside the coil boot is bad. They are easy to check and take off. You can also have someone check them with the proper tool when they are on the car. Otherwise you can take off each coil and have autozone check it with the spring on and the spring off to ceck resistence inthe coil and the spring.

Another problem it the IAC. this is the idle air control. it is also a easy fix. two bolts on the side of the throttle body. before changing and wasting money, you should get it tested as well as the other parts.

injector are probably dirty. try some SEA FOAM injector cleaner. you can put it in the gas tank and crank case wher the oil goes

I alos hook it up to the main brake booster vaccum line. I use a fuel line that is tappered off at both ends. I connect it to the line and the other end into a can of sea foam. it cleans the carbon in the intake also and it is perfectly safe