What you write with nitro.
The head will be somewhere between 7.5 and 9 inches (20 and 24 cm) with 50 - 0 % nitro in factory setting ideal .25 PSI but is independent of the power level, even when the engine is in idle.
Exhaust pressure depends on the power level and is never that high in midrange and for sure not in idle, that's the difference for the standard carburetor I think.
The pressure may drop off on the pump a bit. The regulator is not very precise. But not as much as muffler pressure, the carb suction picks up at idle to make up for the lack of muffler pressure. That is why check valves on the muffler pressure result in the engine quitting after it runs at idle for a minute or two. It is also why the low speed needle is especially sensitive and if not precise you may have to use the bypass plumbing.