I would try to troubleshoot this one on your own. This problem is finicky at best and almost always inconclusive when you try to have a shop "decode" it. You tinkering away and getting your elbows dirty, one thing at a time, will yield better results. Like others have said already, start basic.
The ones that take a bit more elbow grease ....
FPR cleanup/replacement
Cam or Crank sensor replacement (VERY rare but I did have a crank sensor go bad and alter idle)
Manifold gasket
Chances are, 1 of these is the culprit. Hopefully it's one of the ones listed in the first list.
I have just put all of these parts in my watch list on ebay JIC. At 78,000 miles should I have all of these valves (EGR, IAC, PCV) just cleaned or should I start replacing?