posted 2 months ago, asking for a code p0172.
found out to be brake vacuum hoses #31201430
this linked helped a lot : http://forums.swedespeed.com/showthread.php?401201#/topics/401201

2 helps needed.
1. which diameter of an Oetiker clamp do i need?
2. can I just unclog the hose? 120$ is way too expensive.

 

the code is indicative of a vacuum leak so you are on the right path looking for ways to seal up the leak. Any style of clamp should work - you're dealing with a vacuum not oil pressure... but check out PN 978172 on a Volvo web parts store of your choice. More importantly you want to inspect for any cracks on the rubber or plastic parts. You may even want to consider some RTV etc if you see a crack. See this diagram for clamps and seals

https://www.volvopartswebstore.com/p...06/978172.html

 

I appreciate your help mt6127.
Yes. It's something to do with vaccum, and my case it is confirmed that brake booster vaccum hose is clogged.
It also has a line after air filter to intake manifold(thus bypassing MAF sensor). It's the one what's clogged.

I want to reuse it if unclogging is possible.

 

not sure what would clog a vacuum hose - unless the PCV system feeds some oil spray etc. I haven't looked closely to see if there's a check valve etc but I'd think you should be able to work in some brake cleaner and a wire to see if you can find a blockage. With that said, I'd suspect if you had a blocked hose from the engine/vacuum pump up to the booster, you'd have a heavy brake pedal feel and not an idle issue.