I have a 1997 855GLT and want to experiment with bumping up the turbo boost at the wastegate. Has any one experimented, with success, with this procedure?
By adjusting the wastegate on the turbo so that less internal pressure is bled-off, the turbo can be made to generate a higher boost pressure. This mean that the air being forced into the engine's intake manifold will be even denser, which can translate into much higher horsepower levels than usual.
R.E.C.

see following website for procedure:

http://www.easternaerospace.com/automotive/tips&tricks/boost-wastegate/

The max boost is limited by the ecu (unless you really mess it
up to the point where it can;' control he system). Changing the
wastegate as you described seems to allow the turbo to idle at
a higher rpm and you get faster boost response (less lag) but
no additional power. Over do it and the throttle goes from a
linear "ramp" to a toggle switch. The correct setting varies
by year (according to volvo specs) and I bet a lot of them are
not set perfectly from the factory. IPD (www.ipdusa.com) recently
had an article in their newsletter on the procedure for correctly
setting it. They might have it online.

To add more boost you need to change the ECU that limits boost
(chips sets do this) or somehow fool the ecu into thinking it is
seeing less boost then it really is.

Cowboy here's a better way to adjust it. I run mine at 8-psi and its a noticeable improvement. Anything higher and I've gotten the CEL that they mention. You need some 1/4" rubber tubing, a tee fitting for that tubing, a large type syringe or something to generate a little pressure, a fuel pressure gauge to attach off the tee to measure pressure. I used a mechanical fuel pressure test gauge that I got at PepBoys. You can find the syringes there that you use to suck up oils or fluids too.

Good luck........... Mike ....... '95 850T

This is from IPD's website.

BASE WASTEGATE ADJUSTMENT 850 / 70 SERIES Turbo models*

Occasionally we run into cars that do not produce normal boost levels. In
many cases this is due to the fact that the level pre-set at the factory is at the low side or below the factory tolerance.
Although it’s not possible to change the maximum boost level w/o check engine
lights, you can adjust the base wastegate setting to improve bottom end throttle
response and torque. The base setting is about 1.5 psi, you can safely raise this to 6-8 psi. This will give almost instant boost production in response to throttle input. If you over do it, you will have a hard time preventing the tires from spinning on take off so you might have to experiment a bit. You'll need a boost gauge or other accurate low pressure gauge that you can temporarily use to adjust the wastegate. We use a radiator pressure tester / pump that has a built in gauge (Stant brand).
You can get these for around $50 or borrow one or use a
basket ball pump or similar low pressure pump and accurate low presure gauge.
Remove the heat shield above the turbo, disconnect the wastegate actuator line
at the turbo controller valve (TCV) and attach the pump and gauge to this line.
The TCV is usually attached to the air filter housing, it has 3 small diameter
rubber lines attached to it. The line with yellow bands on it is the waste gate
servo signal and is the one to use. The red line is the manifold pressure signal
and the blue line is the bleed line. Make sure your connections are tight, you
don’t want any leaks to cause erroneous adjustments. Disconnect the waste
gate actuator rod form the waste gate lever (C-clip or spring clip). Loosen the
10mm lock nut and shorten the rod so that it exactly lines up and drops over the
closed waste gate lever when 6 psi is applied to the actuator. Note: this
adjustment should be made with the engine cool and not running. Test and
adjust to suit your personal tastes. Do not exceed 8 psi, it won't hurt anything, but performance will be reduced and you will get a check engine lamp as the ECU is sensing that the wastegate is operating beyond the control range of the TCV.