Pass side. Looks like I should have a replacement ready as it's crusty.

Some of the diagrams show a roll over-valve in the evap system. The photos show no hose clamps, typical of evap hoses.

Example:
https://www.volvoclub.org.uk/tech/service/850/VacuumDiagrams-Turbo.pdf

My first guess was that it was a fuel pressure regulator or check valve as the fuel lines come up on the pass side. I'll have look more closely to see where this hose ends up but it's all obscured by bits and pieces of gizmos.

If it was a fuel line I would have expected to see better connections between the hoses and the crusty creature - a bit more than just a slip fit. Plus the hoses look rather vacuum-like with thick rubber but little or no reinforcing.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

Hmmm, very interesting. You may be right about that being a fuel line......

That crusty thing sort of reminds me of something on the old 740/940 Regina fuel systems (single high pressure pump in the fuel tank). It was mounted in the fuel line just above the in-tank pump and it's purpose was to buffer the fuel pump pressure pulsation:

https://www.brickboard.com/FAQ/700-900/ImagesProcedures/Images-ReginaFuelPumpReplacement/regina26.jpg

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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

See part #13 in this diagram:

http://www.volvopartswebstore.com/showAssembly.aspx?ukey_assembly=235159&ukey_make=865&ukey_model=11966&ukey_category=7862

Note it comes with the hoses already attached, so you'll have to chase each hose to their other ends in order to remove/replace. Bring lots of money to the dealer or explore other possible sources.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

pulsation attentuator

From a few years back, fun reading:

https://www.matthewsvolvosite.com/forums/viewtopic.php?t=51523

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Keeping it running is better than buying new

My little crusty would have been $300+ , so I won't try to chase one down on speculation that I'll need it 10 years from now. I'd imagine these rust out and puke fuel at some point. For a NYC area 1995 mine has been spared a lot of salt but still this part is crusty.

If you look at the example in the link that Klaus posted, that one was quite rusty also. If it is so important then why didn't they make it out of stainless steel or something more corrosion resistant than what they used.

I read somewhere, I can't remember where, that they used those things in order to quite the pump action, not because it was necessary to make the car run right. I can't help but wonder what would happen if it was simply removed from the equation. I would ask a good independent Volvo mechanic - not the dealer - if they have tried removing them and what happened.

I think the 850 might have come with a 4 year warantee. For now it is probably too late to try to slow any rust. Coating it would probably just end up trapping moisture.

There would not be much choice other than to bypass it. You guys are brilliant though - I sure somebody still sells these gizmos or something similiar. Have one in the glovebox just incase (ah my glovebox latch broke, is NLA so I just have a glove box hole :))

What you need is a good pick&pull, but even there the 850's are getting scarce.

The newer cars, 1998, have a pulse modulator at the fuel rail. And they moved the pressure regulator to the subframe.

Your car will work nicely without the modulator, just not above 5,000 rpm.

While the 850 uses a baffle to eliminate the fuel pump pulse at high pressure, check out this 4 minute clip. You will be happy to have a 'simple' system.

https://www.youtube.com/watch?v=znEeiLobzxg
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Keeping it running is better than buying new

Also I rarely get my 850 near 5000 rpm so I'm covered. I have plenty of spare cars too so the Volvo can be retired for a year while I search for a part. If this gizmo does rust out it will probably let go slowly so I'll hopefully catch it before needing a tow. Nice that they have this gizmo up front and low so it can blow leaking gas on the cat converter!

Did volvo made the original.

Recently tried to buy Ebrake cable for my 2004 V70 ,
dealer tells me its discontinued,
at some point its not worth them carrying parts the aftmkt sell for 1/3 the price.
Volvo listed cable at $97.
Bought it for $30.

Just take the original volvo part number and google it.

Has this engine ever been out of the car? Just to the rear of the sway bar, you will see 3 lines, two of them go into metal fittings which connect to the fuel rail above the engine. The other one is a vacuum line from the tank to the charcoal filter area.

I suspect that a mechanic cut that line and then just happened to find a 'correct' size connector to continue the vacuum line. There is no 'replacement' part. If you remove it, be prepared to have a suitably sized piece of hose to connect the vacuum lines.

BTW, the 1993 850 had a connector in that position, later models have a single line from the rear of the car to the right front. My 1996 850 had the clutch replaced and the booger cut the line and left me with an EVAP error message. The 1993 at the P&P was a perfect fit!!

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Keeping it running is better than buying new

What little work was either done by volvo or myself. Timing belt, motor mounts, volvo exhaust. the bigger mystery with this car is it has only one o2 sensor. Actually that's why I discovered this little crusty - I was searching underneath for more 02 sensors.

Original owner - and after 22.5 years it only has 122K miles.

I did things like a wheel bearing, control arms, sway bar links, oil changes, motor mounts, batteries, brake cables. I don't think the car has been to an independent mechanic.

The rear O2 sensor is hidden under a plate behind the CAT. Look on the driver's side.
Or, down close to the turbo, on the transmission housing, there should be two connectors for the O2 sensors.
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Keeping it running is better than buying new