I don't turn the wrenches on this one much, when asked to help. I installed the datalogger and review after every event.
I call it staged, but I suppose compound is correct. One feeds the other. Diesels many times run three compound for boost pressures in the 120-160 PSI range.
Now many meth guys are running two small turbos both feeding a larger turbo for the second compression stage. This is an OLD tractor that has been pulling since the 60's in a continual evolution. Pretty cool to know they used to run both NA and turbo on the same day with a carb and quick release fittings on the turbo.
You likely would never see one of these engines anywhere today, so I would not imagine you would recognise the manifold.
Runs Kinsler mechanical fuel injection with pressures in the 140's depending on load and RPM. 2 stage mechanical injection. Some are now 3 stage I think.
I don't know much about the entire sport but have been around this tractor since a kid. Still kills me to know that when they end a run and shut the TB all that air has to back up out of the turbos... OUCH. Talk about compressor surge. I still haven't convinced them to add a BOV. I almost had them convinced to add a water to air IC but they were outlawed shortly after I started bugging them about it. Air temps on the second stage are a little above 400 deg F.
I can't remember the turbo sizes but I think one is like a A9-90 or something and one started out as an Schwitzer S-4D. Both are custom.