FYI, here is a post with similar info for non-turbo versions:

https://www.matthewsvolvosite.com/forums ... =1&t=65002

How to eliminate vacuum leaks

Get a piece of paper.

Draw out your vacuum diagram and size each and every vacuum hose in inside diameter and outside diameter and length.

Go to your FLAPS and buy hoses and clamps

Systematically remove and replace all your hoses on your car.

Repeat every 10 years.

We read here time cand time again.... “ ...the vacuum hoses look ok....” Well, you can see half of them , so how’s can’t they look ok? I chased a rough 4 cylinder idle like an idiot for a year before I did the inspection the right way; removing each hose and plugging/ blowing looking for splits. My ...

In the pic posted below, you will see the IAC valve and the black thing it plugs into directly above the AI. What is that black thing? If you look real good, you'll see that I broke 2 of the capped holes. My engine is running rough now and I think this is the reason. I need to replace the black thin...

The pictures loaded when I was on my computer. Thank you.