I had a non-turbo car before that the catalytic converter crumbled on and blocked the exhaust. It was easy to tell it was blocked by there being no increased exhaust flow when the accelerator was depressed. I am suspecting my cat is going in my 99 A4 1.8T. When I check the exhaust flow, I do get increased flow when the accelerator is depressed, but it is kind of erractic. It takes a few seconds to get a burst of air. Upon releasing the accelerator it immediately drops to very little flow. Is this a sign of a bad cat or is it just how a turbo behaves? The car also idles poorly and often has a hard time start (sort of diesels). Any advice is greatly appreciated. Thanks!

 

Lift that bad boy up and wack the cat with a dead blow hammer or something and see if you can hear crap rolling around in there.