after reading some of the advice on other threads, I managed to survive the whole mission without blowing the engine.
Basically, I kept the throttle back to keep MP in the green always and left rpm around 2700, just changing rpm to around 1800 when in the dive, and going back up to 2700 to climb out. If the oil temp rises, then I just opened the rad oil doors with lalt+s.
If my assumption is right, then the throttle only needs slight adjustment to maintain the desired rpm when speed starts to drop off