Boost issues

[peixcman]

a couple of issues and I think they're related:

2001 Volvo xc70. Parents car, 102K miles. 1. Last week check engine light on. PO234 Engine overboost condition. I shut out the light and it hasn't come back on. They didn't have any more complaints. 2. Tonight I took the car out and at 4000rpm it starts dumping boost, then immediately starts bucking violently. won't rev over 4500rpm period. Drive it 3800 and below it's like normal. Any ideas?

[JRL]

Vacuum leak
Inspect and change out all vacuum lines.
Check the turbo charge pipe for a crack or leak, etc etc

[peixcman]

Is a vacuum leak or broken charge pipe the most common cause of overboost conditions?

[Aviator]

This almost sounds like the catalytic converter is starting to plug up.

Dave.