I had a D3 with a LR RAI and now a D4 with a Safari snorkel. With the driver's window up, there is very little noise with either.
The RAI needs the rubber elbow that goes from the inner guard into the airbox, to be sealed. There are a series of holes in the bottom of that section.
As Tombie says, the inner guard has to be cut to install the Safari one. I have photos from my install here: DISCO3.CO.UK Photo Gallery - Safari Snorkel Install
Having done it once, I would suggest that you get the Safari install done by someone... anyone but yourself! The scars on my forearms have healed, but the mental scars remain. :D

