[vm]

Potential symptoms,
Idles well but looses all power at high RPM's.
General loss of power.
One way to potentially check this issue is to remove the pre-cat O2 sensor and see if there is an improvement. Of course, you will need to clear a code afterward and it's also going to be noisy.

 

[jt2ma71]

loss of power is a big one. Most of the time it will trip a code too. Engine will feel "choked" when you try to acceleration. Ive also seen backfiring into the intake with severly blocked cats.

 

[TMcNasty]

Lethargy...and lots of meowing.