Boost gauge

[bbaspense]

I have a '90 Cummins with the first gen. engine..

Where on the turbo can I hook up a boost gauge?

[fox]

The gauge does not have to go to the turbo , it can and should go to the intake manifold.
I am not sure of your exact configureation, but on the 12 valve inline pump set ups, there is a 1/8 inch tap about mid manifold.
It is horizontal and uses a 10mm wrench if I remember correctly.
If you do not have this tap, then remove the air horn and drill and tap it for the correct nipple.

[BIG RED MACHINE]

Your choice,BB..
Either use the pipe plug in the intake and mount it there,or,tap the air intake horn.I myself,like the air horn being tapped for boost pressure.It will give you,in my opinion, a better sense of what level you are at.Now,before I get flamed on this I'll explain.The pipe plugs found on most 12valve intakes of off center,front or rear,and are very close to the cylinder intake and draw.If it is mounted near that how accurate could it be,pressures there would be on a constant change.your truck,your choice...Andy