Symptoms of a knackered catalytic convertor

[Jodi]

What would the symtoms be of a catalytic convertor gone bad?
1)I am getting the rotten egg smell when rev'd hard.
2)One exhaust vibrators/ moves more than the other when rev'd hard but exhaust mounts are sound
3)Getting vibration through the gearstick and throttle peddle at anything over 50mph

Any views/opinions/recomendations always appreciated.

[Funky Jo]

When my cats were gone, I could mainly
- hear the metallic ratteling coming from loose parts "vibrating" inside the cat housings
- feel the engine struggeling to "freely breathe out" at higher revs

I think the only way to know for sure is lifting her up and see what´s (left) inside...

[SeanyD]

Cat knackered on my Elise a while ago - symptoms were
a) Exhaust/Engine sounding quieter than normal - unable to breathe
b) Rattling sound when returning to idle or turning engine off - honeycombe inside cat had broken loose.
c) Engine not as responsive when hitting the loud pedal.

Got a replacement from a nice PH'er classified, who had de-catted, at about 1/10th the price Lotus were going to charge.