what year/model car is that, and which hose is that? kinda looks like its tucked under a turbo to intercooler hose but hard to say. is that the crankcase breather hose that goes from the oil separator box under the intake manifold into the air intake hose that goes from the MAF to a turbo?

if its a 1992+ 740/940 turbo, thats part 3507424 if its a pre 1991 7/9 turbo, 1276438, ditto a few years before that.

350724: https://www.volvopartswebstore.com/p...1/3507424.html (or any dealer)
1276438: https://www.volvopartswebstore.com/p...4/1276438.html (or ditto, any dealer)