I don't see why it would. I discussed it with my dealer yesterday because the rep noticed it was smoother than his to drive. The techs at the garage thought it was a good idea.
Also if anyone has the new D4 AWD, I had one yesterday whilst my car was in getting polestar. The pipe on that is even tighter than than mine was.

Just fitted a 200mm length of hose, easy job.

I removed the rubber engine cover as its simple to do and does give a little more room for the fingers. Mine had wire around most of the hose length, so I slipped it off and put in the middle of the new one so it looks ok / authentic

Only had a short drive so will know any difference once next week's commuting starts so will add any comments later

The one that came off was 158mm by the way
Driving today = there is a difference!
Not sure how to describe it other than a slightly more responsive / eager engine. Maybe the first smaller turbo starts sooner now, or is already spinning whereas before was idle?
I need to drive a bit more to know I'm not just imagining it, but the engine is smoother somehow?

Has anyone put a vacuum tester on this pipe before and after replacement to measure if this actually improves the vacuum available or monitored and compared MAP values at low revs?

Reading the MAP values before and after a pipe swap is probably the only way to test properly. Plumbing a vac gauge into the pipe will change the length, internal diameter and flow characteristics of the pipe anyway, which would skew results ...

I just took at quick look at mine, its an older 2015 181hp version and the pipe does not look all that tight to me....

Do you think this engine would benefit from the cheap mod?

The tiny little pipe to the right of the braided one (you can just see it) looks to be a much tighter angle, although maybe not providing such a critical role!

https://dl.dropboxusercontent.com/u/...604_150157.jpg

It's hard to say without pushing back the mesh cover on the hose to have a proper look.

The smaller-diameter hose you mention is the vacuum feed into the solenoid from the main vacuum manifold, so that's important too - just check its run and curves to make sure it isn't kinking / folding too much.

Changed mine this morning - didn't notice any difference but I tend to leave in the somewhat asthmatic ECO mode most of the time anyway.

The original hose on mine was about 170mm (2016 model year) so it could be that Volvo have twigged in the factory. Replaced it with one that's 200mm.

Considering how hard it was to get the old pipe off this one went on remarkably easily, so if I get the Tortoise of Despair™ on the drive into work tomorrow I'll know what the problem is...

I wonder what Volvo would say if there was an engine issue which was being rectified under warranty and it required them to look in the area where your have replaced this pipe and they noticed that it had been changed?

Not much, as they would have a hard time proving altering the pipe length 30mm would have ill effects or be classed as a significant change to standard specification to void a warranty.

Now altering the software for more performance, or the air filtration, after market lowering etc these things may cause issues as you have potentially altered the specification significantly.

It is still something to consider.