Remember though that "knocking out the honeycomb" of a failed cat may not have the same results as replacing a functioning cat. What caused the cat you knocked out to fail? If excessive missfires has resulted in a cat overtemp and partially melted the matrix, the cat would have become restrictive.
On the other hand, replacing a functioning cat with a pipe seems to have been tested to be non-productive (according to earlier posts). I haven't tested this, so I'm not arguing one way or the other, just pointing out that for this thread to be meaningful, we need to compare apples to apples, eg replacing good cats with pipes.
