The cylinder head temp gauges I've seen have a sensor that's something of a washer for the spark plug. I've also seen some that clip to the cylinder head fins of an air cooled engine. What's a CHT gauge for a Diesel look like? Where does it mount?

How about a GM MAF temporarily set in place of the cross-over pipe? Do some data logging then scour the internet for conversion factors. That should tell you a bunch about post turbo air flow.

Sixto
91 300SE
87 300SDL
83 300SD ... any takers at $1100?