I'm getting codes 0491 & 0492 which are right and left bank secondary
air system failures.

Once the engine is warm, if i clear the code.  They don't come back.
If it is really cold, I get the code shortly after starting, but again
if I clear it, it won;t come back.

Without Audi specific test equipment, what can I do to trouble shoot?

Fuse is good, vacuum lines all look good.

The other components are the blower, ECM, Solinoid, combi-valves.  I
get both the righ and left banks so I believe it to be a fault in a
part of the system that will throw both faults.  Don;t think it could
be a simultaneous right and left combi-valve failure.

No other codes.  2001 A8L, 4.2L AUX Engine.

Any thoughts?