Have been having misfiring on acceleration troubles in my TE Magna 3 litre V6. I think Ive tracked it down to leaking exhaust manifold and engine pipe gaskets. Ive also found the cat converter guts have disintegrated and been blown into the rear muffler, but there is exhaust coming out the rear, so its not totally blocked.

The troubles all started after the auto failed and thumped the engine around a lot, enough to stuff the drivers side engine mount, which has been replaced. I think the cat was damaged then from the backfiring that occured.

Im wondering if the new manifold gaskets go on dry or with sealant?

Also, Im wondering what usually happens when the cat shatters and is blown down the exhaust..... does it clog something up or does it mostly blow out? And Im wondering how a manifold/exhaust leak cause it to die on acceleration, Im thinking maybe it upsets the readings of the oxygen sensor, thus affecting the injector operation etc. Im also wondering if having a cat with no insides will affect performance in any way?