I've been having some problems with my 04 Beetle (2.0L).

My original problem was that I was throwing a catalytic converter code, so I replaced the bad converter with a universal converter. Within a few days the new converter had already been burned up and the light came back on. At that point I did a tune up (plugs and wires) and replaced the cat again (with the same one under warranty).

Now I'm stuck in the same situation but worse. I'm throwing the following codes

P0411 16795 Secondary Air Injection System Incorrect Flow Detected
P0420 16804 Catalyst System, Bank1 Efficiency Below Threshold

I figured that the cat has been burned up again, but why do I keep burning up these brand new converters over and over again. And as far as the air injection code, I'm kind of in the dark on that one. Is that related the the converter codes that I keep having, or could that be a separate issue all together?

I've been trying to get this figured out for a month now and I've got just about nowhere. I have had a few other car savvy friends look at it as well and they are clueless too.

Any pointers in the right direction would be great
Thanks for the help