Service advice please

[Jinx]

In the next few weeks Bill will be
Making a appointment to have
The check engine light code checked.

The code is po491 and Po492
Secondary air insufficient flow
Bank one and two. In reading
Up on this I find it can be a pain
To find the cause of the problem.

We use a few independent guys
Which of course are cheaper than
The local Porsche dealer. My question
Is knowing that the dealer has the
Correct instruments and hopefully
The knowledge to fit the problem
Or problems. Would it be better to
Use the dealer vs the independent
In this case.

Thanks in advance for you opinion.

Bill and Jinx