1. I had a BOV on my 1999 S70 AWD. I have an automatic transmission. I don't think it did anything bad over the time I had it installed, but over a longer period of time I could see it casuing problems.

http://www.asashop.org/autoinc/JULY/TECH2TEC.HTM
http://auto.howstuffworks.com/question257.htm

2. Yes people have put BOV's on their Volvo's automatic and manual transmissions alike. There is no performance gain from them on our cars what so ever. They are there for looks and sound.

3. On a T5 17PSI to 20PSI is ok I would air on the safer side and go with 17PSI. Some people will tell you they will run 20 PSI all day and be fine. Ok that might have worked for them but it might not for you. Also before you mod your car be sure you have STAGE ZERO done and that means getting your car up and running the way it should be from the factory if not better. A better I mean silicone vaccum lines, silicone turbo hoses, which are better then the OEM versions. This is just a start with what is better then OEM. If your going to raise your boost do it the proper way with an ECU upgrade. Don't fiddle with a MBC.

 

Im not looking for a preformance gain just the sound. And my volvo only has 70,000 miles on it so it should be in pretty good shape still
NIck

 

Um I hate to tell you but you still better do STAGE ZERO. Trust me on this one.

You want the sound just get an EST intake.

 

So for the stage zero you have to replace......

 

Sorry but does anyone search anymore?

stage zero "tuning" list and if ur car lacks performance...

Full stage 0 list:

Plugs
cap/rotor
oil/transflush
filter (oil)
hoses (the little vac lines)
samco hose kit (Turbo Models ONLY)
02 sensors
fuel pumps
clean injectors
clean IC/IC plumbing (Turbo Models ONLY)
Air filter
plug wires

This is right from my Resources thread in General Volvo. You need to check that thread out ASAP.