Getting CEL's 17831 and 17819 for insufficient air flow; Secondary Injection system, both banks. The air pump mounted on the rear of the intake manifold runs for a short while after startup. I'm not hearing what used to be a throaty exhaust sound for several minutes after cold startup. There would be a definate change of sound when it cut off. All plumbing to the Kombi valves is good and tight. Any ideas here? How do the Kombi valves work? Also, while running thru the blocks tonight on the VAG, I developed a code 17987: Throttle Actuator adaptation not started. Did I induce this fault? If so, what can I do to fix it? The code comes right back after VAG reset

from the valves.

The is a T that splits the vacuum lines to the combi valves. It cracks often.

I have an A6 2.7T. I just hauled out the SAI pump to make sure the bearings were not seized. It's not too hard to do. If you're not getting enuf air, the pump may be seizing up......... hundreds and hundreds of bucks for a new pump. Fuk that unless it's totally kaput.

On the output side of the secondary air pump, blow gently down that T-hose. If you can blow into it, then the combi valves are defective (or one of them is anyways). Those valves are one way only and you should not be able to blow them open.

There's more beyond that for this emmission system. I haven't gotten beyond this point yet.