lol, I did the same when I set up my guages. Spent an hour going over everything because I couldnt see any boost in the drive way. You have to get her out on the road and drive. Then you will get what you are looking for.
And like Simon said , its on the left hand side of the column under the dash.

Just used it this morning after a BREAKDOWN (my first F250 let down) to read codes.

Left side driver footwell, mounted directly at the edge of the plastic dash, socket is point down towards the floor, from underneath it just looks like a black oblong 1cmx5cm - slip off the cover to reveal the connector pins...