This is a look at the proper location for drilling and tapping for the boost gauge on a 6.0L if the "T" fitting installation isn't desired.  This location for the boost gauge eliminates the rattling noise sometimes associated with boost gauges on the 6.0L Powerstroke.  A 90 degree compression fitting is used in this application.  Thread size is 1/8"NPT.  Requires a size "R" drill bit (0.339" or 21/64"). Refer to the tap for the exact size (most have it printed on their shank).   This is just an optional method for those who don't wish to use the "T" fitting kit shown in the previous image.
Torque Spec. for the 4 bolts on the intake elbow is 23 ft. lbs.
NOTE: If you don't have this 90° Fitting, you can still use the straight fitting that comes with most tubing kits.  Simply drill/tap at the 11 O'clock position in this image (above the upper L bolt)