To explain it somewhat better...
At position 1, i'm at 11000 ft altitude, going some 110Kts at around 2000 rpm and leaned for maximum RPM
At position 2, near the PR NDB, I throttle back to 1500 RPM, mixture stays the same
At position 3 I begin the descent (FIX 13 is around 8000 ft)
When descending in the turn, i can decrease RPM in 2 different ways: by adjusting the throttle or by adjusting mixture.
When i change the throttle, i need to increase throttle again near FIX 17, to keep the RPM constant when entering the glideslope.
When i use the mixture, i don't have to increase throttle to keep the RPM constant from position 2 on. Only in the glideslope i have to adjust the throttle
The aircraft i use is the Il-103, somewhat strange modelled in FS, because it starts to waggle 20Kts from the maximum published cruise speed and is able to fly some 2000ft higher than published.
It has a fixed pitch prop, and 200hp engine power