Swirl flaps = absolute nightmare. I had a Saab 9-3 with the GM 150 diesel engine and a swirl flap broke and dropped into the engine doing £1100 in damage.
There are two different types - plastic flaps that drop off and damage your engine as above, and new, improved, stainless steel ones that drop off and destroy your engine completely.
I swore I'd never risk buying another car with them fitted, but I've just gone and bought an Alfa GT with the same engine. I will be removing the swirl flaps and probably blanking off the EGR valve while I'm at it as soon as possible. I'm hoping to be able to do it myself but there are specialists who can do it -
http://www.autolusso.co.uk/swirl-flap.html
Typical symptoms of swirl flap problems are that the car will go into 'limp home' mode and won't rev above a fast idle. It might well clear after being parked up but once you've got the early symptoms it's only a matter of time before the engine cuts out completely and won't start again.
Good luck!