Lack of power & rough idle at any temp

[HSB]

Hi, my Volvo V70 D5 2003, 100k miles, is suffering from lack of power and rough idle. There's no obvious pattern, but I've noted the following:
- happens at any temperature - cold or after several hours driving
- car idles fairly rough - any gear, any temp
- loses power (is it called limp home mode?) for several minutes on at least 2-3 occasions on every drive
- this power loss is especially prevalent when going uphill, accelerating (e.g. joining motorway), or general overtaking
- however, 80% of the time, the car works fine and goes pretty fast like it's supposed to!
- despite the rough idle, rev counter doesn't appear to deviate
- a mechanic has checked hoses to/from the turbo, says they're fine
- fuel filter was changed 1.5 years ago, around 11k miles
- specialist garage said error codes pointed to a vacuum leak - they eliminated the hoses to one of the engine mounts but apparently couldn't reach the other one.

I'd really appreciate any help. I've had so many different suggestions (intercooler, MAF sensor, ETM, fuel filter) but honestly don't have the cash to replace all. I average 30k work miles a year so need it working properly. I'm based in West Yorkshire and London, got the car only a few months ago. If anyone can recommend a specialist who can find the problem without replacing several-expensive-items before getting to the root cause, I'd welcome a recommendation (sorry to the forum moderator if I'm not allowed to ask things like this - I honestly just need help!)

Thanks in advance for any responses.
HSB.

[Georgeandkira]

Hello, "...they eliminated the hoses to one of the motor mounts but apparently couldn't reach the other one." is one of the strangest things I've ever read. Get the codes from them (or the bill) and post them. Also ask for clarification on the hoses they removed. Did this happen before you owned the car? Also you can try cleaning the MAF sensor. Being careful not to touch the grid, you spray it with MAF cleaner. Let it dry for an hour or two, I've read. Clean the contacts of it's plug. Buy a code reader or find someone who has one. Pulling those numbers straightaway is quite a help. Get a reader which reads CAN protocol. Many bargain readers do not. Good luck. Kira

[225-50R16]

I am sorry but I have to delete my message cause I made a mistake.

[HSB]

Hi, thanks for the response.

Went back to the garage and they listed error code 6805 - turbo / boost problem. I also asked them again about their "elimination and reach" for the vacuum hoses. They checked by disconnecting from the engine mounts (or something to that effect - my inaccuracies in detailing this correctly), but didn't repeat the statement about not reaching one of the mounts. Not sure why they originally said that or what they meant?

I did a quick internet search for this error code and ran across a forum thread where drivers have experienced the same issues, with the D5 engine(s). They suggested:

* get all vac lines checked for leaks (vac test or smoke test) = already done, intercooler was reported to be OK.
* check engine pads for leaks = done by elimination, although I must say the car does seem to judder a bit, maybe that's just a rough idle from a dodgy injector?
* check / replace turbo control valve (TCV) on air box = ???
* check / replace turbo governor valve on front of engine block = ???
* last resort its the turbo = ???

Not sure what to do. Need to sell the car soon as well due to other commitments. Help!

Thanks.