does anyone know if adding this http://www.ipdusa.com/Volvo-940960/P...p-136-277-827/(ipd boost actuator) increases my risk of blowing the rear main seal, head gaaskets, or any other gasket?

 

That only replaces the one you have from the factory.
It is adjustable so if you adjust it to much you increase the boost pressure for the turbo and that could damage the motor.
But There should be no problem If you were to just swap them for it is probably set to the factory setting (5-8psi).

 

will i notice a difference in performance? I am not clear on how it actually works, or what it does?

 

There is a little nipple on the the turbos compressor housing (cold side)and there is a hose which connects that nipple to another nipple to the wastegate actuator. The wastegate actuator regulats thepressure the turbo compressor makes by opening the wastegate in the exhaust housing (hot side)of the turbo and lets some of the exhaust exit throught that hole instead of applyingall the exhaust gases to the turbine. If youadjust the wastegate actuator, then you can getone of two things:1) you get more boost from tightenin the rod, or 2)youget less boost fromlosening the rod.

You will get more power ifyou run more PSI, butyou will want to get an aftermarket boost guage so you know what PSI you are at (a safe level is ~10-12psi).

 

I boughta MBC so I can run more boost: