Helping a friend - input needed!
 

Hello all,
As you can see from my low post average I am a new member here. I am familiar with an array of different vehicles and am looking into at some point picking up a used S4 as a track car. Anyway, I am more familiar with my cars (BMW's) but do have some knowledge with turbo vehicles.

Here is the problem:
My friend drives an 04 A6 2.7T, Automatic. The car drives really well; however we have started to notice that when it is decelerating only between around 2,000rpm down to about 1,000rpm it sputters slightly. It's nothing more than an inconvenience at this point, and the car still feels great under full load, but I don't want it to escalate into a bigger problem either.

My thoughts:
At first I thought it could have been a pin hole in a vacuum hose, or hose leading out of the bypass valve, but since the car doesn't do this at higher RPM under deceleration it rules that out in my mind. Perhaps an intake problem? Leaky intake hose?

I am sure you are all better versed in Audi diagnoses than I am so I would love to hear some opinions. Thank you in advance for input!

Define "sputter". Does it miss? What happens when you accelerate from this low rpm?

Have you pulled any codes?

By sputter I mean just a slight irratic RPM move between 2,000 down to 1,000 rpm. It is great under acceleration and doesn't pull any codes. Doesn't feel like it misses at all, just bounces the RPM needle by a few hundred rpm between 2 - 1000 rpms...

deceleration sputter 1-2000 rpm??

Since you see nothing on acceleration it is probably just the emission control system catching up so you don't polute our air... Vacuum leaks would be most noticable on acceleration and if bad enough throw a code.