Howdy...........welcome to the mad house. I can't find the link atm but I recall that another member (with an FG) used the .82 rear and reported that it spooled from idle ----- which actually probably means that boost was there from 12 or 15 hundred rpm but ran out a bit 'up top'. With your 3.9 gearing, I reckon that you may as well take First gear out of the box if you want to actually go forward when you start off.