I have a '95 855 turbo wagon, about the same mileage as yours. What you're describing sounds like a leaking hose. Inspect all the clamps and condition of the rubber hose sections from the turbo to the intercooler and then to the throttle body. Don't be alarmed by a little oil present at the hose junctions, a mist or a few drops seems to be normal. Also check the underside of the intercooler for cracks/holes.

About the wastegate rod, I'd strongly suggest not adjusting it. Search the forum for the topic. You'll find a few posts about new connecting rods. There's a possibility it has been misadjusted by a previous owner and it's dumping pressure.

If you can't find any suspect hoses, have your Volvo mechanic check operation of the wastegate control valve (mounted on the side of the airbox) at which time he can check for proper actuator rod setting.

I know I'll get flamed, but if I wanted a car with more than 220hp I'd have bought one. Frankly, overtaxing the tranny's in these cars would seem to be the reason one should seriously consider the "benefits" of more power.

Good luck,
--
Erwin in Memphis, '95 855t

First, about the control rod: your ECU will detect the new control rod position and adjust immediately. It's just a waste of time for a momentary benefit; there are other ways to achieve higher boost if you care to risk it. Turn it too far, and the ECU will simply shut off your engine. (Plenty more about this in the FAQs at http://www.tme.com)

Boost gauge position is normal, and here's why. Your engine will briefly pull up 20lbs of vacuum...so the gauge is evenly divided between approximately +20 and -20psi. But maximum stock boost is about 11psi, or halfway into the white. (This gauge should really be called a manifold pressure gauge.)

The rush of air has two possible sources: first, if it happens when you take your foot off the gas suddenly, there's a blow off valve that has to drain boost pressure. Otherwise, second, (my opinion) you're hearing the increase volume of air and exhaust gases flowing through the compression and exhaust plumbing. I've been hearing this rush in all my T-bricks: 745T, 945T, and now S70T5. (When you're in a jet, if you listen over the roar of the engines, you can hear the rush of air against the skin of the aircraft. Air and gases compressed by a turbine spinning at 200,000rpm into a tightly confined space would likewise generate pneumatic noise.)

You could look for a loose hose, but since your boost is normal I doubt you'll find anything wrong.
--
David (98 S70 T5SE Black, misc mods (mostly lighting), red calipers) (92 940GLE)

if you find no leaks, try adjusting your wastegate 2-4 turns. if you want the boost higher, do another turn. just dont over do it.
regards

Temp gauge slightly above half is normal.

You might check all the hoses on the high pressure side of the turbo.
They have been known to blow off. Check the various clamps (pulling
out the air box intake tube running from front of grill to under the
air box makes this easier -- intake tube simply pulls out, no tools
required).

My 98 turbo makes a sound similar to air leaking, too. You probably
don't have a problem but the hoses are easy to check.