Congrats to the new owner, that's certainly a low mileage car! Pics, please - when you get it running like it should!
I doubt that vac line you are showing is causing the turbo to not run, the pic is too dark to tell where it came from though. There is a line thar runs straight from a small nipple on the intake manifold over to the switchover valve and eventually supplys boost to the ALDA. That needs to be in place or it won't run well.
The carbon buildup in the ALDA line is not as bad on these engines, for one thing because the way the manifold is situated way over to the other side from the turbo, most of the crud collects in the crossover pipe.
There's a lot of vac lines on this engine, esp on the left side! The ones around the EGR are better plugged for testing purposes
My 603 didn't run well at all because the turbo wastegate flapper was clogged partially open. Removing it and a good clean out with a screwdriver, plenty of elbow grease and some liquid wrench (WD40 would also probably have worked) and the car ran like a scalded rabbit
A wastegate partially stuck open will dump the boost as if the turbo isn't working when in actuality it is. If the turbo bearings are loose either radially or axially, then its time for a rebuild.
Does yours still have the trap (football shaped) topside, on the turbo outlet?
If so these can get plugged up so bad the car will not even run and before that the car will run very poorly. The trap oxidizer was a lousy idea. The replacement is a Cat oxidizer under the car and this is a lot more reliable but these have also been known to get plugged up after lots of slow around town driving.
The 603 engines need frequent Italian tune ups (ie. run the engine WOT as far as you can without getting a speeding ticket!)