Having had cases like this with previous rs4's we had an idea what would be causing the engine managment light to be on.
But the first thing to do was take the car for a test drive to get an idea on the idling issue/lack of power. We then plugged the diagnostic machine in and read out the stored faults, The faults stored pointed to carbon build up in the inlet manifold, which is what we had suspected and is a common fault with VAG fsi petrol engines.
Unfortunately a new manifold was required in this case. We carried out a full valve de-coke before fitting a new manifold from Audi.
Whilst the Audi RS4 was with us we carried out a longlife service and fitted a cat-back miltek stainless steel exhaust system to unleash the sound of that Audi V8!
