Sound exactly like EGR valve to me - common problem on Mjet engines in my experience as my Stilo had 3 in 4 years. I had a turbo pipe split and there's usually a whistling/air rush sound accompanying that, so try flooring it from idle in 2nd with the windows down and stereo off. If you can hear anything untoward then it could be piping.
If you can avoid taking it to the stealers there's a simple EGR valve test that requires a socket set, 20mins, and a sardine tin lid (or any metal lid if you don't like sardines!0
Technical: EGR valve - remove, clean & modify. - The FIAT Forum
This should cure the power problems, save you £75 in diagnosis, and a reconditioned one is picked up for around £25 on ebay then fitted in 20mins, as opposed to £250 from the stealers (£175 part, £75 labour - FOR 20 MINUTES?!?!
Last summer on vacation in France, that turbo pipe you describe (the pipe from the turbo manifold to the EGR) actually came off
my turbo with a big *BANG* while departing 'enthusiastically' from a tank-stop. A crack/leak will make it sluggish, but when it removes itself from the turbo you will definitely not go anywhere fast
About 80 km/hr was its top speed as the turbo was completely by-passed
At the time I really thought I killed my car btw, luckily the French 'Depannage' guy fixed it MacGuyver style..
Ow and how easy it is to fix it depends on the engine type.. On the older JTDs it's in front of the engine, but on my 150hp 2.4 it is somewhere in the back, and the pipe that's bolted to the manifold is almost impossible to remove. To reach to lower bolt is a nightmare.. So I still run the MacGuyver solution..