Pros: it's louder, holds boost longer, supposidly this is the way it was supposed to be installed.
Cons: It is holding boost longer than it was designed and you could cause
comprespor surge, it will make the most annoying pinging sound (unless your into that).
This is a quote from Tom at Forge Motorsports:
"Running the valves reversed can help as all pressure/boost acts linearly, you don't push a spring sideways do you. We are reliably informed by VAG senior engineers that the reason the OEM bosch valves are fitted the way they are IS because of the noise, as reported above the valves when reversed are slightly more audible. In the original position they are less efficient but quieter."
Here is another good source of info for you, just click on "Installing the DV in reverse?" on the right side.
I have never tried it personally, but other people that have didn't show any power increases. One guy who ran before, and after block 120 graphs actually lost some power. People claim smoother acceleration, and incresed boost, it seems to vary from car to car.
[ November 19, 2003: Message edited by: Josh Fryauff ]
I did it for a while and it did seem to hold a bit more boost maybe.....I have nothing to prove this though. I switched it back though because it sounds pretty girlie when reversed, and a $50 mbc will accomplish the same thing as fas as holding more boost.
Mine has been backwards for a while now. Ever since I replaced my Greddy BOV with the Forge DV. I installed the Forge the same way as the BOV. On the Passats the DV is upsidedown, which means the vacuum hose has to loop back up to attach to the nipple. On the MKIV's installation looks pretty straight forward because the vacuum hose is where it belongs