Wastegate is normally closed until boost pressure on the servo opens it, so a broken line gives you too much boost -- if the overboost protection switchover valve is working, it will dump the boost signal to the ALDA and you will only notice it if you get surging as the overboost opens and closes. You won't ever get low boost unless something is wrong with the turbo.

Catalyst supports are very tough, they usually only break up from serious impact damage or severe overheating/rapid cooling -- this could happen, I suppose, if the overboost protection cycled a lot a full throttle, but is more likely to be from other causes the produce lots of soot or unburned fuel in the exhaust.

Your turbo should be OK if there are no marks on the turbine from flying ceramic chunks. The restriction in the exhaust would cause low boost and power loss by itself, the turbo wasn't getting decent flow and couldn't produce any boost that way.

You need to replace or remove the catalyst, though -- if one chunk came out, more will follow until the whole support is gone.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!