This same question was discussed here not long ago. Although both ETMs and MAF meters are THE most common problem causing idle fluctuations (even w/o codes) and a MAF meter can be easily installed as a "try me" attempt before assuming something more serious, like what I'm listing here below, IF the car was built before 1/02 production date and non-turbo, have your dealer refer to TNN 43-38 as that MIGHT BE the solution. I have never seen a need to do that yet in our dealership but the problem is known with a solution.

If that doesn't apply to your car, has the dealer tech tryed calling the tech hot line? If the problem can be duplicated (not intermittant), they should be able to fix it.

There are other known TSBs on the subject too as idle, surge related problems with newer cars are hardly rare these days. Sometimes it's a software upgrade too.

Here's the older thread :http://www.brickboard.com/AWD/index.htm?id=696690