I have a 2000 A6 Quattro, 2.8. I keep getting the code for EVAP flow incorrect. I changed the fuel cap, since it's the easiest and cheapest attempt. Ibought the factory Audi service manual for this issue, but it just shows the components and the location of them. No diagnostic procedures. I clear the code, and within 1 hour it's back. The car is original, never been hit or damaged, about 75,000 miles on it. I've had this problem since I bought the car with 68,000 miles on it. My lead foot daughter blew up the engine at about 73,000. I replaced the short block, and redone the heads, so I know all my vacuum lines in the engine compartment are good. I don't want to just start changing EVAP components till I hit one that changes it, That gets quite costly. Any common issues that can point me in the right direction to start with? Thanx in advance for any light you can shed on this.

you can put your ear by the left rear wheel well. I think thats where it is on your car. your listining for a pulsing sound. kind of like a beat. if you dont hear it, it might be that your LDP leak detection pump, is bad. since that should have kicked a differnt code its probably not that, but could be. if you dont hear it, dont suspect something to be wrong right away, that pump doesnt always run. but if you hear it, then you know its good. what you need is an audi scanner to run some diagnosis on it, but this is some driveway work here so give it a chance, its better than nothing. next find the evap hose runing out of the manifold that goes to you N80 valve. thats your evap purge regulator valve. it will look like a small round plastic piece that is covering the solenoid. it will have an electrical connector on it, and it should only be a short distance away from the manifold on the hose. thats the best description i can give you. disconnect the hose going to the evap canister, but leave the one connected to the mainfold. with the engine running put your finger over the open end of the valve and see if you can feel the vacuum from the engine while it is being pulsed on and off. this it does more often than running the LDP so you should be able to find out if its working within a few minutes of running the engine. if you cant feel the vacuum its probably a mechanical failure in the valve. this is what i suspect to be the case. if you cant find the valve give me your vin and ill show you a picture of where it is and what it looks like.

Is the code 16825, P0441 ? "EVAP Emission Contr Sys. Incorrect Purge Flow" ? This is quite common on that engine. I would re-check all you vacuum lines, the original Audi ones are quite brittle. I moved one on my engine, the hose cracked and threw that code on the next ride, replaced the hose to get rid of the code.
Also check the suction pump at back of engine, top, near the firewall,