Small leak at the gasket before the catalytic converter.
 

I found the leak when seafoaming the intake (smoke out of the gasket). Does this leak influence performeance? It's time for me to order a few oil filters. If this must be fixed, I will order the gasket together. My concern is how hard it is to get the bolts off, as they are there at high temperature for years. Thanks.

gaskets will usually let a little smoke by with Seafoam. Unless you see fluid...
 

coming out or hear an exhaust leak, I wouldn't worry.

no biggie... thats normal. mine did it too

Thanks. There was indeed only a very little smoke. So it's OK.

Re: Small leak at the gasket before the catalytic converter.
 

I too had an exhaust leak at the cat. A friend is an Audi master mechanic and here's what he told me. "The exhaust leak would allow cold air to hit the turbo, which (for some reason) would kill it.

Now i thought it sounded stupid so I ignored it for a long time. When ended up replacing the gasket, and tightening the bolts back down,,,,no turbo. I'm not an audi mechanic (so keep that in mind), just telling you my experience.

99 A4...250,000 miles.

fix? short of replacing all the parts surrounding the black mess?