pressure issues seem to be the #2 issue in the Volvo Performance world,
beaten out only by vacuum leaks. Boost pressure control in the
1994-1998 models is a pretty simple system but for the ECU to manage
boost correctly it relies heavily on known base values and settings. If
these settings are off or if there are mechanical issues then the boost
control system can be out of whack.
are great devices and by and large can provide decent performance
upgrades, however there are some issue to be aware of before simply
installing one. Since the ECU is no longer in control of boost and the
MBC will allow boost to develop as fast as the turbo can provide it (up
to the adjusted target) you're flowing quite a bit more air and
consequently have more load against the engine than the ECU is tuned
for. This means you may have too much timing and not enough fuel in the
early part of the RPM band where you really need it. This is the primary
source of how and why MBC's can damage these engines, specifically with
respect to bending rods or spinning rod bearings.