So after trying various things troubleshooting this damn buzzing vibration noise at WOT after full warm-up, it seems to boil down to the cats. I've replaced mufflers, removed tips, checked heat shields, etc.

Noise only used to occur in 1st briefly if I was WOT off the line and after car was warmed up. Gradually it got worse. There is no mechanical 'feel' associated with the noise.
Now, it makes the noise after car is warmed up at 3/4 WOT and all the way through 1st, 2nd and into 3rd. If car is cold it does not do it much. If I let off the throttle the noise stops, and it is not rpm dependent.

Have appointment next week at Porsche BH to inspect cats. If it is the cats, good news is they are still under original factory warranty of 7yr/70k miles. Will post how it tuns out.

 

how many miles do you have?

 

8 years or 80K miles.

when they are really bad, they will throw a CEL with code 2098.

 

35k miles on the clock. Service manager looked it up in the computer- I also thought it was 8/80 but apparently it is 7/70..

 

Sounds like the 'honeycomb' in the cat broke. That won't throw a CEL just rattles like crazy at certain frequency.

 

Mine just started sounding like that. Threw code 2098. I'm thinking about the AWE cats. The dealer said the warranty is 8/80. Mine's not covered cause its not the original cats that are on it.

 

ok so just got my car back from dealer to replace a busted tranny mount.

get this- the funky rattle noise that I thought were bad cats is gone!! More than likely the tranny was slightly shifted and under any torque was touching a heat shield or something. Anyway, cats are fine.
Very odd because from the tone and placement of the noise you would have sworn up one side and down the other that it was coming from the exhaust system.

Anyway glad that annoyance is over, back to driving....